Mike, Paul I've got to disagree. The STC takes a standard C85 to a whole new level! I've flown an O-200 power Champ, C-85 and then my Super-85 Champ back to back, and the differences are amazing. All three airplanes were close in weight and prop pitch; combo leaning towards the cruise side.
The Super-85 got off the ground quickest at 300ft, C85 broke around 450-500 and the O-200 was the worst breaking ground at 700ft. Super-85 climbed the best: 1000agl by the end of the runway (3000ft), C85 - 500agl, O-200 - 450agl. At full power cruise the Super-85 and O-200 were equal at 115mph, and the C85 was about 10mph slower.
Sorry it's taken me so long to write back. Summer time has me on the road 5-6 days a week with little or no time for the internet.
You've seen the threads where I've talked about building my engine, so you can see where I could have saved a bunch of money. First off, I had to find a C-85 to start with, which you've already got. Plus I got a new set of mufflers and bought a new prop. If I had been in a situation like you (already have a complete C85 and accessories) it would have cost about 5-6k to rebuild it with the O-200 STC.
As for Don Swords, sure he's a sales man and trying to make his dollar, but the numbers he gave you are solid. Take a look at the power curves and you can see it yourself. If you've got the money and don't want to rebuild the motor yourself, having Don's shop build it up is a good deal. I have several friends using his Super-85's. Don also mentored me when I was building up my engine; I stopped by his shop everyday because I didn't know how to do something, or I messed up.... like breaking rings.
Flow matching the cylinders is worth it too. The only reason it cost so much is because of the labor involved. I think I spent 4 nights and 20 hours smoothing out the intake elbows and spider with a mini dremel and brake cylinder hone.
I'm trying to remember, you've got a C-85-12 right? If so, for the STC you'd need an O-200 crank, Rods, and Pistons. A serviceable crank can be found at any salvage yard, or if you're a wheeler-dealer, buy a whole O-200 and part it out on eBay or something. I heard of several people doing that and getting the crank and rods for a net of $0. Aircraft Specialties has their own version of the C85/O-200 STC and sell it for around $300. They can also get brand new O-200 cranks for around $2700.
If I was in your position, I'd opt for a new crank, swap your rods with Aircraft Specialties, and put 4 brand new ECI CermiNickle Cylinders on. You said your IA was busy for a while, but you really don't need him too much; time wise, if you wanted to build the engine yourself. You can break the engine apart, clean everything up and send off all the parts for inspection and certification. Aircraft Specialties also carries all the parts you'll need for a rebuild...i.e. bearings, gaskets etc... When you get all the parts back from the shop(s) and the new parts bought; take them all down to the FBO and start bolting it together. The overhaul manual is very through and will walk you through every step. Novices like me and you can bolt an engine together in 2 eight hour days, if all the parts and hardware are there. That's one weekend if you don't goof off. At a shop like Don's, they can build the engine and have it running on the test stand in 8 hours.
Think it over Jim, but I'm pushing for the Super-85. You won't be disappointed, I promise! If you've got any questions, let them fly, there's probably several others wondering the say thing.
If you're ever around Atlanta or Macon, give me a holler and I'll take you in a Super-85 powered Cub unless I get my Champ flying by then.