There's a lot of good ones and a lot of bombs out there too.
Some of my favorites:

Ford 351 , 370, 391.
International 549 (Gallon's to the mile, baby!).

Had some fun back in the day with:
Ch*vy 350 and M*par 318

I've got three trucks with 5.4 modular v8.
I'm happy with them, (great mileage), but they still need to prove themselves to me.

Diesels are great!!