I actually bought a spare FF IO-360-A1A that I am overhauling now as a fun long term project. I just did a TOH on my current motor with OH’ed cylinders, and it’s not making metal (knock knock), so I won’t be swapping in the new motor until the old one gives me a reason, but I pondered a lot of the same decisions as you during the process.
I chose to go with New Lycoming Cylinders this time around simply for the fact that I wanted to start fresh on this build. The problem with OH’ed, is usually don’t have an idea of what you are getting unless they rework your exact cylinders, if they are even serviceable. I am still on the wait list at Airpower, which I have been on since January. I should see them by next summer based on the 18 months lead time I was quoted. I do plan to send them to Ly-Con for a port and polish, alodine treatment, but will Cerakote them myself when they get back to match the rest of the motor instead of having them paint the barrels and leave the alodine finish on the fins . I am a huge fan of Cerakote, the cooling benefits alone are far superior to paint, and I like the look of the finish. I Cerakoted the crankcase, sump, accessory case, all the brackets, the entire exhaust (muffler included), intake tubes, valve covers, all the brackets, the starter ring gear etc. Kinda went a little nuts, but after I spent way too much on a blast cabinet and the new massive industrial air compressor I needed to run it continuously, I was going to get my money’s worth. lol Should be one sharp looking motor when its done.
I had my mushroom tappets DLC coated at Airworx in lieu of roller lifters, largely due to cost but I also believe that DLC will solve the Lycoming cam issues of past. If it’s in the budget, roller engines are super smooth, and having the ability to swap a lifter w/o splitting the crankcase is clutch.
I did have the Ly-Con O-Ring Mod done on the new case after it was overhauled to avoid leaks in the future. My current case has a heavy dose of sealant running the entire length of the spline, so obviously leaks were an issue previously for someone. Based on the excellent reviews from aerobatic guys that have been running them hard for thousands of hours now, IMO it was a no brainer and far superior to the silk thread method which will eventually leak. It’s my understanding you don’t use any sealant on the case halves with the O-Ring Mod, but I will double check with them before we assemble to be sure. I also ordered a few extra o-rings in case they become unobtanium in the future.
Good luck on the build, it’s been super fun and wildly informative for me.
Billy