I didn't think you'd be interested in the bike, I was thinking the engine mods. I raced the bike for a couple of years after i built it. I raced against mainly RZ/RD 350 Yamahas, and other 600cc 4-strokes (Kawasaki 4's and Ducati twins). I sold the bike to a mate who also raced it for a year and then he had an offer he couldn't refuse for the genuine TZ500H rolling chassis. He went on to race CBR600's and I went onto TZ Yamahas.
He sold my Honda race engine to another friend of ours who never used it for anything and I eventually bought it back and shoved it in my old 500-4.
When I built it I had a std cam welded and reprofiled by Joy cams, The GPZ305 pistons were installed by NGK racing (they did massive overbore Turbo drag bikes at the time).
The gearbox and clutch mods, all the gas flowing, combustion chamber re-shaping, valve enlarging, exhaust headers, carb mods, ignition mods, etc etc I did myself. It was a bloody quick bike and was all done properly, cost me a fortune in measuring equipment, burretes, scales, bore guages and the like. I tried about 5 camshaft profiles...believe it or not I settled on one not that far off a stock CB650.
Even minus its bigger carbs and pipes its quick in that old bike. You dont see many rusty old 500-4's doing over 125mph - especially with a dicky screen and top box...hahaha
I guess I've covered it all there really...not much to see inside that will stand out particularly. Before I built the 600 I raced a Dixon racing Yoshimura 460. Its interesting to see what people are doing to these things now especially as times have moved on.