4 Speed w/ Overdrive Any Good?

I agree with what's been said so far.

The OD units are not as strong as the standard 833's, but they're still plenty strong enough. The gear spacing is a little wide, so its not a good drag racing transmission. But I know of more than one person that runs them behind a 440.

The bearing retainer is too big, you'll have to find a way around that by machining something.

And, never in a million years would I pay $650 for one. EVER. I have three, I think the most I paid was $200, one was $150 and the last one I bought for $80. Nothing wrong with any of them.