Yeah, the cooling issue would be a bit too much work to be worth it.
Since I'll be using an entirely different EFI system (MegaSquirt), the distributor and ignition issues don't matter. I could work out the fuel issues and all that if the Thor upper would mate to my existing lower.... but if I have to use the Thor lower and alter the cooling system, it becomes too much of a hassle. Maybe if I go with a 4.0 or 4.6 in the future, but that gets beyond the inexpensive and versatile concept that I am working on.
Since you seem to have a good bit knowledge, does the new Performance Distribtuors DUI systems fit into a NAS 3.9 block? (www.performancedistributors.com
). A bit pricey for my blood, but I would think a 1987 distributor would be the same physically as a 1994. Given the issues that the Lucas ignition gives folks, going to the GM HEI would be a definite improvement.