95 E300D, trying to learn about the brakes and suspension parts

[Texasgeezer]

Sometime, probably in the next couple of months, I want to do some work on the brake system and suspension.

(1.) In looking at the w124performance.com website 'brakes' section and one of the Mercedes EPC websites, they both show the brake booster to have the same part # for the non-v8 w124's. Why wouldn't any of the brake master cylinders listed for earlier years bolt up to my booster? I would like to use one that has a repair kit available.

(2.) In reading about brakes it appears that a single piston caliper can be more reliable than multiple piston calipers and have about the same stopping force ( if the brake pad area is close to the same ). So is there much advantage ( stopping ability ) to going to the E320 rotor, caliper, and pads compared to the E300D's rotor, caliper, and pads?

(3.) Mercedes seems to be out of stock for my right front control arm. The few places that have one available have increased the part price quite a bit. That's part of the reason I've been looking at the E320 parts.

If I go to the E320 control arms, what other parts have to be replaced to have the E320 control arm fit properly. First glance shows the splash shield, rotor, caliper, pads.

The rear suspension is really confusing. New bushings appear to still be available from Mercedes. Which ones are good candidates for rebuilding? Do the 'smaller' arms use the same pair/part#s of bushings ( inner & hub )?