The RZ engine shares the same bore x stroke as a banshee same cases clutch ..shit like that
The main differences are power valved cylinders which are controlled by ignition / pv controller / servo motor - cables.. the RZ cylinders have higher port timings in stock trim then a Banshee netting them more power.. U.S. models being rated in the mid 50's and the later Canadian models being rated in the low 60's.
They have better shift forks (roller guide pins rather then solid guide pins for the banshee), they have a wide ratio transmission, have a higher output stator for the bikes lighting system, they ave a better ignition curve then the banshee - a lil more aggressive and with 4* more advance built into the CDI.
The early RZ cases had extra holes in the cases where the mechanical tach drive was driven (they are just bosses in the banshee cases - back top) and the RZ had an oil pump driven off from the water pump for oil injection.
With a good ATV type port job, you should be able to net 75 - 80 hp with ease and there are aftermarket ignition system / power valve controllers out there to dial them in to pipe / carb, riding style, port job configurations.
I have a set ported by Jim of Passion Racing Engines ( 4 mil 12 port RZ cylinders with a hot Dune port durations ) that Jim claims will be possibly high 70's maybe low 80's.
I hope I have covered everything you are asking,
Mike