what m/c to use

I went through the problem of getting the correct M/C for my Cuda a couple yrs. ago. The first one I got was the small/small resovoir one like you got and it didn't work well. Then I got one for a 74 Dart with disc brakes. It was the style with the big resovoir in the rear. The first 2 I got were rebuilt and not very good. Actually IMO they were junk. After I looked online at Napa's website I found a brand new one they could get for just $15 more. I ordered it and had it in 2 days and since it's brand new it works great. Sorry I don't remember the part # anymore but just go to www.napaonline.com and put in 74 Dart with disc brakes and it will come up with different M/Cyls. to choose from. Then you can take that number down to your local Napa and order it.