Chevy C10 brake booster

[wrangler160]

Keith I do not know the GVW on the truck. They truck has been very confusing. The title says it is a 3/4 ton however it is a short/wide bed that came with a 305 so I don't see how it could be a 3/4 ton. The VIN on the dash is rusted so it is very hard to read. I am going to try to find a way to clean it so that I can check it against what’s on the title. Also it has the 11" rear brake shoes; however there is a brake bar in the setup and the guy at the parts store said the brake bar was only for the 11 3/4 inch brakes. So it saying that the booster is a J50 just threw me for another loop. I did hear that the JB5 is the more popular of the brake boosters. Thanks for your help.