well i am from the school of getting old and wishing i had so here is my pick of a engine .
454 BBC or the 8.1L vortec . . . there both power house animals .
my good friend had a truck just like mine but short bed & 454 big block . i had a built 400 sbc in mine . we took off red light racing one day and he got me off the line hard with the big block low end power but my 400 sbc got him on top end rpm pull .
so if you want GRUNT power go BIG or go home . if you like rpm then go high winding sbc stuff .