I put a RPI lightened flywheel on the 3.5 I built. Now I am using a 3.9 with stock Rover flywheel. Not much difference it seemed to Me. I have never driven a completely balanced Rover V8. For My use it doesn't seem necessary. One of the unique items on My +8 Bitsa is the use of a T5 Borg Warner transmission. This necessitated a GM clutch. It is much bigger and heavier (both in weight and difficulty in pushing the clutch pedal) than a standard Rover clutch. I changed my clutch master from a 3/4" to a 11/16" and that helped (internal clutch slave).
But IMO still too stiff. My friend Loretta, who has/drives a '58 +4 and a '71 XKE says My +8 Bitsa is not driveable. At least by Her.
