I have a 70 chevelle and my question is this:original drum/drum car I converted to front disc using parts not a kit.I got a disc/drum master from napa it is 1 1/8" bore removed my original it is 1 1/16" the inside hole diameter and depth are the same so that all seems like it will work .But the lines coming out of m/c are different size with different fitting threads .But they are opposite front port is large on one and small on the other and rear is large on one and small on the other.?Please fill me in:confused::confused:

ttt:confused:

As far as I know, the "stock" drum master cyl should have a 1" bore with the flare fittings for the brake lines on the driver's side. Front-most flare fitting is the smaller one with 1/2"-20 threads and the Rear-most flare fitting is the larger one with 9/16"-18 threads. Does this sound like what you took off?

Disc master cyl would be a 1+1/8" bore with the flare fittings in the same arrangement.

Poke around at NAPA online and compare pics and info:
http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=430&CatId=3&SubCatId=3

Sounds like either your new master cyl or the old one might be non-stock, but that doesn't mean they won't work....