One thing to keep in mind, well 2 actually:
1: It can be difficult to beat the price on a crate motor by building one yourself. Crate motors have become very reasonably priced, and have good quality parts (depending on vendor)
2: You get a warranty on a crate motor.
Look at Scoggin Dickey parts center or Jim Pace etc....
The ONLY reasons to build yourself would be if you want a very specific build spec (performance goals that aren't offered as a crate), or to be able to say,"Yeah, I built that!!"
Tim