No reason to tear into the motor. I have had very good luck buying motors like this and putting them straight into cars. I always change the timing belt and rear main seal. Thats about it. One of my rb's even came from Venus. The one in my car now is another bone stock motor, never taken apart and makes ~650 rwhp and runs well into the 9's at over 140mph in the 1/4. It won't last forever running like that but it's a damn good motor for now. lol
I would definately take a chance and stick the motor in as is. Once it's running, if you decide it needs work, then pull it back out and go through it.
It's suprising to hear the comments about Venus. Anyone I know that has gotten a motor from them has been very happy with them, including myself.
Jon