Spoken from first hand experience, it will cost you almost as much to rebuild a motor the right way as it will cost you to buy a nice crate motor. Notice how I underlined 'right way'...by that I mean not skimping on machine work, and all good quality parts and components, and assembled by a professional maintaining all proper tolerances.

If you want to rebuild for the experience of it, go for it, its kinda fun to build stuff like that. I really enjoyed the builds I did. But if you just want a nice motor for a similar price, and without the extra work, then go for a crate motor.