I would shift at 6800-7000. The hp curve is pretty flat from 6500-up, so anywhere you shift, you're still going to fall back into some power. The bottom end is solid, so if you feel like you have to string it out a few hundred rpm past that, you're fine. We pulled it to 7200 on each pull on the dyno, and yes it did sound good up there. I'll send you a video.
When you get really serious about racing, send it back and we'll put some compression into it...this is an easy 525-530 hp engine with the right combo of parts.
Still though, with a mismatched cam, and pump gas compression, 1.43 hp/ci isn't anything to sneeze about.
Run 110 gas in it, and run Brad Penn
oil in it. A 40-50 weight
oil on the hot side is what I would use. It takes this little motor forever to get up to operating temperature, so be VERY ginger with it until it gets up to
oil temp. The main bearing clearances are set at around .0017-.0018 so it's a little on the tight side until it gets hot.
I installed the pilot bearing. Left the thermostat out, but will ship it with the engine. Don't forget to run thread sealant on the flywheel bolts....they hit oil.