Is there a difference in master cylinders?

[chevy garage]

I running new brake lines on my 70 for manual disc conversion. The two lines from master cylinder to proportioning valve are not lining up. I bought a new master cylinder for a 71 and the line inlets measure 3". The distance of the new line spacing is +/- 4.25". Am I using the wrong master cylinder or not?

Thanks

[MrGoodpliers]

The '71 master cylinder should work fine. More importantly, you need a disc brake (71-72) proportioning valve.

[chevy garage]

I thing I have the correct proportioning valve. I bought it from our local GM dealer and it looks like others I have seen. I don't know what the problem may be. I noticed a different looking master cylinder in the Early Classics Catalog. It looked like the line outlets on the master cylinder were further apart,which is what I need. Our local parts stores only show 1 listing for 71 pickups with disc brakes.

[boraxman]

If youre using Inline tube lines they wont match up to the stock prop valve. I ended up buying one of their prop valves, but I havent got it yet....so we'll see.