I'm gonna toss another monkey wrench in here, if you all don't mind.

I have had two "not-so-good" experiences with GM crate motors, that were supposed to be "plug 'em in and run 'em" setups. the first one was by far the worst, but I wound up with a very good engine, after I screwed up big time. I bought a "TargetMaster 350, in 1981, uncrated it and dressed it out to install. When I tried to put my flywheel onto the crank, I could not get the bolts to line up. So, instead of tearing all of the work I already had in it off, I just put it back on the stand, flipped it over and yanked the crank out, and took it - along with the flywheel, and the crank from my old 350 - back to the dealer where I'd gotten the engine. After a lot of discussing, and cussing, a Chevy Factory Rep who was visiting on the premises, got involved, and they found that they had a whole truckload of engines with cranks that were drilled wrong. Chevy wound up giving me a new crank - the only one that they had in stock at the dealer at the time was a forged item, - and forgave me for not just bringing the whole thing back. Now, it gets better. I was getting ready to put the new crank in, and noticed some grit of some sort laying in one of the bearings; turned out to be casting sand. Investigation showed that the engine was full of the stuff - I collected almost a quart of it off of the driveway, after the cleanup was done. Well, long story-short, I tore the whole thing down, popped the soft plugs and galley plugs, washed and cleaned it up, had the rotating assembly balanced, cammed it, and basically blueprinted it. Got a real good engine out of it. If I'd been able to just stuff it and run it, it would have eaten itself alive.

The other incident was a friends big block crate engine that would not balance. It was a 454, and should have been a slam dunk replacement, but on start up, we thought it was going to vibrate itself to pieces. Replaced balancer and flywheel to no avail, and finally wound up giving it back to Chevy in exchange for a new one; it (the new one) worked just fine.

So now, I am quite cautious, and a bit skeptical, about crate motors. My preference leans toward a custom build, no matter how pricey (within reason, of course).