I have install a 97 rearend into a 85 firebird with drum everthing is together now, but the combination valve and master cylinder. My old valve looks like the one in the picture. I bought one from here and it was an aluminum valve but I don't know what years it was from. Anyway the only lines that match up is shown in the last picture. I was thinking just to cut the lines and reflare, but I don't have enough line on the top to master cylinder. I see eds valves im not sure if any will be a direct swap.

 

Your old cast iron combination valve not only mounts to the lines differently as you've discovered, but it also has SAE threads; later valves are metric. The standard alum valve has M1.0 tube nut threads until early 1989, then changes.

83 is considered the end of the above valve, but some creep in apparently. Note what Ed Miller has to say about them:

http://www.flynbye.com/catalog/i40.html

JamesC

 

Well im thinking my new aluminum one is 90 on up because it is 1.5. The cast valve that I posted has m8 and 10 threads going into it. Im going to by an 86 to 89 valve, but im still going to have to change some fittings.