Hi Dave,
There are a number of engine options for a Sexton. 6V53 Detroit will fit in with a radiator with very little modification. You wont break any land speed records, but it will move you around reliably. A 6V71 or 6V92 will fit, but you have to cut a larger hole in the hull division plate and find some way of getting a rad in. Diesel is also a lot safer in that enclosed engine compartment. Then there is the big block auto engine option with a special 2:1 transfer case to fit it in without cutting the division plate. I have looked into all these options for my Sexton, and have decided to bite the bullet and rebuild the radial to reinstall. This will keep it original, but maybe not too economical to run.

Perry