Alright! Everything in in place and the car is running! So far I'm really happy with the upgrade. The torque is up by a million and I don't have to floor it just to get the car moving. You can see in the pics that I used a cable instead of the linkage. Everything is actually not in place in the pics and quite prototypic, but it works fine. I mounted a bracket with the cable to the steering box. This turned out to be the best mounting position without any major fiddling. When I accelerate the cable is pulled upwards by the extended lower arm. I used the original mounting point for the linkage between the carbs and mounted the cable there. The bare wire sticking up between the carbs is just the end of the wire before I snipped it.
Although, there are some small issues. The synchronisation is almost impossible because air is drawn through one or two of the butterfly valves at idle. Also, the power kind of stops at 4000rpm. No problem to rev and even make the tires screech in 1st gear. But at highway speed I start to loose power.
I'll fix the butterflies and install a fuel pressure gauge. I'm running the mechanical fuel pump and I have no idea what kind of pressure it delivers. If correct sync and fuel pressure does not cure it I'll start to play around with jetting.
Regarding the turtleback: Hood clearance is not a problem for the 1438 because it's significantly lower than the 2L. The 1608 should of course work fine as well under a hood with bumps. However, it's the clearance in the back of the engine bay that is my problem. I would like to move my engine forward by almost an inch just to be sure that the turtleback fits. That is strange. You can actually see in one of the pics that there is some new red paint exactly where the turtleback hits. So I guess that some PO probably had one mounted. I'll see if I can manage to fit it somehow. Half of the pleasure with the IDFs are the sound, but they are quite noisy..