miles have nothing to do with how the motor runs. i bet some of us on here have 150k mile cars that run awesome because we did regular maintenance.

id find anything less than 75k miles in a junkyard and call it good. and there is no reason why you wouldnt install some other goodies while the motor is out. realisitically if you needed anything it would be just the block. i bet your heads and up are just fine.