Matt,
That's a great question...I bid on a used O-320 engine, involved in an accident (prop strike), on eBay, which turned out to be junk.
If I had to do it again, I might go with an O-360...Still, the eBay engine only cost me $1400, including shipping, and came with a high compression piston STC and logbooks. Graham's Aircraft Engines, in Griffin, Ga., gave me a $1000 trade in credit for my old engine core and sold me a first run (2000 hour) E2J purchased from a state collage flying school.
Graham's re-certified the Crank, parts and rebuilt the cylinders for me. They sent out the original case to be reworked and re-certified (Divco) after I could not get a 337 to use an E2J with Del-Air's STC (anyone left out there who still thinks common sense is involved in FAA decisions?).
The biggest savings was having a good friend who is an A&P IA, rebuilds lots of lycomings and was willing to help/show me how to rebuild mine.
I would also be remiss if I did not give credit to Harry (DelAir) who has provided lots of information and spent lots of time on the phone with someone who still has not paid for/ordered the STC...(check will be in the mail this week)...I cannot recommend him more highly!!!
Back to the first part of your question; I doubt there is much difference between the weight of an O-320 vs an O-360 (even a couple pounds does make a difference though) however, this engine will still put out plenty (lots) of power and, keep in mind, I'm still using a beefed up 152 engine mount.
Further, I have reduced the weight as much as possible by eliminating the vacuum system, installing a light weight starter, alternator and "permanently" installing only the required VFR instruments (my removable EFIS/electronic flight bag is a whole "nother" discussion).
When I'm finished I hope to be near the same weight as the originally "loaded down" O-200A. I also plan on posting a detailed description of my installation, including the required additional parts, costs and problems encountered.
