I would do it if I were you. In total we have three trucks at home. One fixed up and 2 that could be restored (2 Mercurys I think, but maybe 3), but they would take a lot of work. I believe that truck has the small 6 in it like you said. The radiator looks small and it is a 7.5" rear end. I think anything with the 240 had a 9" and a larger radiator. Just for my input, this is the first truck I've seen with a rear bumper, all that we have at home don't have one.
Trevor
P.S. If anyone has a good Mercury tailgate let me know and check out my dad's 65 Mercury at
http://www.cardomain.com/memberpage/556263/2