Some very good points have been made for both options, here's some more food for thought. Right now the MBX4 is a semi hot property as a basis for an MT conversion so you may have better luck offing it as a roller to someone interested in converting it. A good used 4 should bring around $250 to $300, but if you have a pristine example it could bring a bit more. Sell the engine, a good VO1 is worth it's weight in gold at the moment. While it's true some are wary of unknown used engines, many of the OS faithful would roll the bones these days on a chance at a good used VO1 with the current state of the OS buggy engine program being what it is. I've seen these engines go used for as much as $250 in the last few months, but $150 to $175 is average. Another $180 or so on the electronics. The body is another $20 or so and depending on what kind of pipe you have, add another $25 to $75.