You don't mention your transmission choice. You might want to look into a later model inline 6 along with a T-5 5 speed. A 4.3 V6 or a V8 can be done it takes lots of work to do. The steering box is in the way for one thing. If you do a later inline 6 you have to fabricate mounts but things may be more friendly. The pros and cons have been discussed many times here and it boils down to how much effort you want to put into it, and how much $$ you have available for the project.