Well I can't answer all your questions but when you get a crate motor you don't know what your getting. I am not saying all crate motors are bad but when you build it yourself you know what all is in it clear down the the last bolt. I have read bad stories about people getting crate motors with holes that where stripped out things not put on right etc. I have heard good things about the gm crate motors though but they are build down in mexico etc. I had wondered the same thing and eventually I just got a haynes manual and dvd's on building a sbc motor and I took my parts too the machine shop to get done what needed done and built it with my dad so I know it was all done right. As far as value on the car etc I would not have a clue.