I also had a set of these on one of my 65's and they do fit real nice but they have been discontinued for 30+ years so finding a set will be tough. I had a stock master cylinder on that car also.
Post some photos of your car,
I have the Headman Hustlers and I had no issues with fit on my car. The only modifications I done to the headers was I relocated the little tabs that hold the header halves together. The only thing with the car that needed work is I had to notch the upper portion of the shock mount above the shock which was easy and minimal.
Getting them on and off is easy as well, I had them on and off a dozen times while I was mocking the car together. The right side just requires the engine to be raised about a 1/2" and the left side does need the master cylinder to be loose or removed. But I have my fender wells cut close to the headers with only about an 1 1/2" clearance or less around them, if your fender wells are cut out larger or removed then you shouldn't have to mess with the master cylinder at all. Another thing is I'm running Edlebrock heads which are bulkier and that makes it a little harder, I had mocked it up with stock heads and it went a lot easier.