could a 396 in a \'73 K5 be original?? I'm looking at a prospect K5 with a 396 big block and I'm just wondering if that could have been ordered stock or put in by someone else. Thanks for the help! Pete '89 GMC Jimmy- 355, 700r4, 6" Front springs, custom 6" rear shackle flip, D44 w/10 bolt knuckles, 14FF rear. Need- Raptor, Ox locker, '73 tub, ect.