Is there a difference between v6 to v8 brake master cylinders? Or are they different for the different years etc? Any info would be great. I do know about the disc rear proportioning valve difference, but are they also different with respect to the v6 to v8 as well?

Thanks

As far as I know the v6 and v8 M/C is the same

Yep, the same. And I don't think you could get a V6 with rear discs... I put 'em on my V6 car, and used the V8 master cylinder with the V8 prop valve, no problems...

J50 = master cylinder, 82-88, rear drum
J65 = master cylinder, 82-88, rear disc
* note, 82-83 are SAE threads/flares, 84-92 are metric

J50 = master cylinder, 89-92, all brake systems

All the brake systems are the same between "same years" of V6 & V8... that includes brake hoses, caliper pistons, brake lines, etc...