You need to know the crankshaft sprocket teeth and the clutch drive teeth (25/56 on both 350 and 500). That gives a reduction ratio of 2.24 as far as the gearbox, same for both engine sizes.

The final drive sprocket teeth (16 on a 350, 17 on a 500) and the rear wheel sprocket (38 on both 350 and 500) gives chain drive ratios of 38/16 = 2.375 for a 350 and 38/17 = 2.235 for a 500.

Overall drive ratios:

350 = 2.24 x 2.375 = 5.32

500 = 2.24 x 2.235 = 5.01

Assuming the rear tyre of a 19" rim is 26" in effective diameter as it sits on the road (i.e. rolling radius x 2):

A standard 350 is doing 4127 rpm in top at 60 mph.

A standard 500 is doing 3886 rpm in top at 60 mph.

(My 350 is slightly different again due to non standard rear sprocket sizes; I reckon it's doing 4,054 rpm at 60 mph).

If you would like to experiment a bit, use this calculator:

https://www.omnicalculator.com/everyday-life/rpm