I have been thinking I can just mount a full plate of 1/8" alum across the stock seat mounts & mount the new sliders to it.

It all depends how the hole pattern lines up, I know my new sliders have holes 11" front to back & the stock is 12"
But I havn't mounted the sliders to the seats to measure the distance side to side, hopefully that is similar & I can use atleast 2 of the stock mount holes & won't need the plate.

I did a little measuring of the stock mounting points in the car, the seats mount in the same location on both sides but there is a diffence in the heights of the mounts. The drivers seat mounts are 1/4" lower in the front & 3/4" lower in the back compared to the passenger side. My seats came w/ 1/2" spaces so I'm thinking if I only use them on the drivers side (maybe just on the rear mounts) the seats should be close to the same height. My car is a '78 & this may not be true for other models.

Let us know what you figure out.

I think my game plan right now is to just use steel strips\plate on the bottom of the new seat, without the spacers, attached to the stock sliders. I think that solves all the problems.

The fiat sliders are also like 1/8th lower, which might be a good thing.

I hadn't even thought of going that direction & plating the seat & using the stock sliders, Hmmmmmm

I just set it up tonight as I was imagining - Had to drill one new hole in the stock Fiat sliders (not sure why only one side needed it, maybe just lucky\bad measuring...) I need to change around a lot of the hardware for it to work better. I also could have done a better job with lining things up, but I was in a hurry to check out the height and function.

The only issue using the stock sliders is the front mounting bolts are hidden and basically impossible to get at once the seat is in place - you have to do the rear first, then the front.

Everything fits and works okay the way it is, but I really think I am going to have the stock seat brackets welded to the cross bars I made, to eliminate the nuts\bolts that hold it together now (and add height and cause other problems with the sliders...)

I also might make another pass at it using the sliders that came with the seats. It's just an incredibly frustrating process, and the sliders that came with the seats are a LOT harder to work with than the stock Fiat stuff...

Couldn't deal with how high the seat was when using the stock mounting points... I messed up one thing that might help me get it lower, but here is how it now sits. Ignore the bad tack welds, the better welds are on the other side of the brackets...

(Lever\handle is upsideown\backwards - this is what I messed up, the seat needed to be lifted a little extra to work the handle. I thought this was the only way I could mount the handle\brackets without hitting anything.)

Narrowed brackets:


New lower mounting points in the car...


I think it looks pretty good with the roll bar - the top of the seat is still a few inches below the top of the roll bar. without the rollbar, they look like they stick up too high:



More to come soon; a bunch of new problems have crept up to take care of.

One problem that seems to be nearly fixed, is the jetting of my DFEV - Some larger idle jets (was 55/50 now 65/55) have the car movin' out much better...

I've got seats similar to that in my '72. Mine are as low as possible, without creating a new floor. I removed the stock seat mounts and the crossmember from the floorpan, (they were rusty junk anyway). The seats are bolted thru the floor with no sliders whatsoever. Works great for me, I guess short people can't drive my car, (I don't want anyone driving it anyway). I should attach a crossmember underneath to make up for the one I removed, but I don't know if I'll get around to it or not.

This is exactly what I was working on today!
Mine have the sames mounting system & I went thru similar issues.

VERSION 1.0
I first plated across the stock mounts & mounted the seats w/ the sliders & the spacers (so the release bar would work when pulled up) & they sat too high. I was able to bolt the outside slider directly to the stock holes & bolt the inside slider thru the plate which moved the seat out of center 1/2" to the inside, that didn't work either.

VERSION 2.0
Now I have drilled & tapped & relocated the bolt holes in the seats more toward the center (kinda like you did but bolt on)
I mounted the seats directly to plates on top of the stock risers w/o the sliders, bolts threaded from inside-out of seat to make studs so I can just nut them from bottom of the plates
They sit real good height wise & are mounted where I can reach the pedals just right.
There is no adjustment this way but the wife & I are about the same height so they shouldn't need to

I like the way you lowered the cross bars between the stock mounts to be able to mount the sliders with the seats mounted lower, GOOD THINKIN'.
I may have to do the same in the future if my non-slider set-up becomes an issue. Version 3.0?

Thanks for the info on your solution, I'll post mine up in my thread w/ pics when I get all my bugs worked out & completed.
The whole "how to mount non-stock seats low enough" issue seems to be a big topic (at least for those doing it) that every solution we figure out should be of help to the next guy.

PS great thread, keep it coming!

I actually am going to go back and mount the passenger seat permanantly. I welded up cross rails again for the passenger, but with the catalytic converter bump, there isn't as much room for the sliders. Seat sits about 1/2" higher than the drivers side. Can't really tell, except that with the rollbar, your eyes have a reference point for the top of the seat, and it is easy to spot the difference. Annoying.



I've had some fits and starts with some of the work I've done so far... Still have some things to re-do, but I'm putting on new brake calipers right now, and I hope that will allow me to start driving the car back and forth to work safely... Of course, I will need a new clutch very soon too. It never freaking ends...

Do you know the material for the stock seat mounts? Are they aluminum as well?

Question:

Do you have a Backseat with the Roll Bar? or did you do the Back Storage Area thingie?