The way I see it, the YZ360A/B was the hot ticket in Yamahaville prior to 1975 even though it was based on the humble DT1/RT1 core. It's not a major engineering mountain to climb to get the RT2MX up to YZ360 performance specs. Sure, the transmission ratio's are different and the YZ's trick clutch and primary drive are hard to locate but as far as the cylinder, head and cases go, the RT2MX can easily be made to achieve YZ type HP figures despite what the sceptics will tell you. The wheels are the same as the YZ and while the forks might look different externally, are as close to identical internally as you can get. I've currently got YZ250A, MX250, DT2MX and DT250 forks apart and they're all within a cooee of being identical internally. I'm getting Uncle Frank to machine the brackets off the DT2MX forks so they'll resemble the YZ forks externally. The DT250 forks came from America fitted with Race-Tech emulators and special springs and they've got the nod to be fitted to the Hindall RT2MX, I'll possibly get Frank to machine the brackets and a layer of superflous alloy from then as well. All of the 'problems' Over the Hill related are there but the kick starter gear and strain on the main bearing area are reduced by using a later CDI ignition....less effort to start the cranky buggers. With points ignition this is a major problem. The Achilles heal is the stupid plastic worm gear clutch actuator but I'm looking at trying to modify a steel XS650 worm gear which I've been told turns the clutch movement into a "hot knife into butter' scenario.
Over the Hill has also identified one of the problems in the RT2MX in the pipe needing some more centre section. The problem seems to be that the factory used the identical same pipe on both the 250 and 360, showing that they weren't quite on top of exhaust technology in 1972. I've got a period Torque Engineering cone pipe for my RT2MX and it has a fatter and longer centre section. I'm certain that some modern pipe technology by GMC or someone else could improve the exhaust function far better again.
The MX360 is a good solid engine that really isn't all that different from the earlier motor inside except for the horsepower draining balancer. I had an SC500 fitted with a 360 5 speed gearbox and no balancer and it didn't shake itself to bits. In fact Brian Clarkson had a very similar set up in his SC500 road racer and it worked a treat.