[Bob Putnam]

Lou,

Yes, the GM station wagon size was about 2.75" OD. Ulitimately, there's no advantage to one size or the other if the master cylinder is sized for a given travel at the pedal. If you need more fluid at the caliper, you'll need a bigger master cylinder to feed it.

Our "stock" master cylinder size is matched to the 2.375" caliper for the best front-to-rear brake balance, but if you're satisfied with the pedal travel and the rear brakes are working "enough" you could stick with what you have now. Unfortunately, I don't have part numbers for the larger calipers, but they fit mid-size mid-70s GM wagons.