Master cyinder- Brake booster replacement

[Ehodg66]

I'm looking to replace my old (and worn out) Master cylinder and Brake booster. I plan on using a newer model master cylinder but have a few questions.

The PO's who did the frame off rebuild on my 82 truck had an 87 donor truck, they used the interior and the bed, from what I've been told. They also installed an 89 suburban 373 rear end w/ larger brakes. I'm not sure if they used the master cyl and booster from the 87 or possibly the suburban.

When I look in side my glove box, the info label has J5 next to brakes but via info from a few sites, the master cylinder I have is JB7-JD7. My booster is 11" diameter. (pic attached of my setup)

I do not claim to be a brake guru and want to make sure I'm installing the proper booster. Is there anything I should know regarding replacing the booster because of the 89 rear end? Does it matter?

Lastly, I've been looking everywhere for a zinc coated or painted NEW booster and the only one I've found is on CJ pony for 242.99. (pic attached) Any site suggestions would be much appreciated.
thank you