[mgarblik]

It looks like you have enough good parts and seals to put it back together after you clean it up and remove the rust. If your concerned about compatibility of the pistons, one area to check closely is the depth of the counterbore where the booster rod contacts. It needs to be the same depth, +- about .010". If different, I would reuse the old piston. That can effect the ability of the chambers to refill when you release the brake or give you a low pedal or possibly even give you light full time apply if off by enough.

I have had a few situations recently, finding parts and castings that look correct. 1. 1973 SD-455 TA. Wanted a MC that looked exactly the same with the bleeders on the casting. Ended up buying 2 different reproduction MC's and mixed and matched parts to get a great looking and functioning unit. OE casting was rusted beyond honing. 2. 1962 Catalina, power Delco brakes. A new, correct MC was not available, period. This one year MC used a weird wing nut cap and I wanted to retain the correct look. This one I had to send to White Post Restorations in Virginia. It had to be bored, and sleeved with a bronze sleeve. Then honed and drilled for the fluid passages. They do this process daily. Took 3-4 weeks and did a beautiful job. Works great. Perfection comes at a price. Had to bite the bullet and pay $250.00 to have it sleeved and machined. So there is a solution to almost any problem, although it can get a little costly and inconvenient. Looks like you have this one under control now. Good luck with it.