What sort of booster are we talking about here? The Lockheed types have a good track record. The Girling MK2As are much maligned, because they tend to fail and are difficult to successfully rebuild.

However, MANY brickboarders use boosters in general. A few use the Gilring units, and quite a few use other types. I use a girling in my 220. Seems to work ok,

My original booster failed long before I bought the car, and when reuilding it, I noticed that it had a cracked casting. I picked up a working unit on eBay a while back. I bolted it right on and it seems to function fine. I'm told that a completed failed unit = no brakes. My brakes work, but if this booster is working, I've not noticed any great improvement in my brakes. I'm probably going to use the rebuild kit I have for it at some point. But ideally, I'd rather use a standard booster like the type in the 1800.

Old Kombi has a rebuilt/improved girling unit. The fellow in Peru (Amazon Rojo... name escapes me) has a lockheed or something similar.

So, boosters are not necessary, but brake improvement with one could be marginal.
If you have a working unit, hook it up and see if it works. Unless you install a leaking non-functional unit and take it into traffic, it won't hurt anything to try it out.

A complete setup should look like Old Kombi's engine compartment (check the image gallery).

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1967 P220 (My every-other-daily driver...), 1971 P1800 (The Parts Car), 1972 145S (1993-1997), 1977 245 DL (1993-1999), 1983 245 (1998-2001), 1986 745 GLE (1997-2005), 1990 740 GL (2003-4), 1995 945 (2005-Present)....