I'm not a DIY'er but have a good mechanic so these may be viable options. But where do you find a good used engine and how do you ensure that it's good????

This is a nice So Calif car (no rust) w/ 5spd and BBS rims but needs a few items (a few dents, front busings). I had planned on selling it and thought that it needed a valve job as it was going thru a quart of oil every 500 miles. Turns out that it probably needs an engine rebuild (ahgg!). Would it be best to put in a less expensive rebuilt engine (Bavarian?) or to try to sell as is?? Any other suggestions as how to get the most money for my 6er?? Any advice will be appreciated (other than to keep it as, for a number of reasons, I just can't.) Thanks (and I certainly appreciate the tone of this board. It's a world of difference from the E-36 board that I also monitor) PS I hope this ins't a double post as I tried to send a similar message last night but didn't see it on the board....