That Diamond T was built by Weaver Customs in Sandy, UT.
Check out their facebook page. Lots of picks on there. I think it is a compound turbo p-pumped 12 valve built by Industrial Injection.
LS !!! If it's free, use factory truck stuff and put a snail (or two) on it. There are guys on performance trucks dot net getting 500+ to the wheels on turbo 4.8's! With a turbo and fuel, maybe a cam. LS all the way. I think it suits the truck better than the 12v anyway.