Baker throwout bearing dimensions.
Extreme Thread Necromancy warning, but this thread is the best fit rather than making a fresh post.
I was curious so per GPO03FatBoys post I Ebayed these ramps:
25604-00A-inner
25605-00A-outer
I then picked up a Baker Heavy Duty Throwout Bearing Kit as the stock bearing is feculent, and measured the spotface with digital calipers.
If you spotface your reduced effort ramp .985" diameter x .100" deep it will fit the Baker bearing assembly. I'll be doing that next week so I snapped a pic tonight for comparison. Same amount of meat so no worry about weakening the part.
Per Baker literature their kit includes the early style ball ramps, so this mod will get you Baker bearing goodness with lower clutch effort.
I've not seen the back of a Muller ramp to measure, but if it's not already faced to take a larger bearing you could do the same thing or have it done easily at a local machine shop.
The machined washers in the Baker kit as well as the HD kit are what centers the pushrod, so someone wanting an even larger bearing need only make suitable washers then spotface their ramp of choice to suit.