Cheap and easy would be to rebuild or replace the original unit with the stock type parts. But if you're looking to upgrade, and aren't concerned about 100% originality, going to an aftermarket dual circuit, preferrably boosted, master cylider would be a good upgrade. Tey can be had for 4 wheel drum systems without too much cost. I beleive virtually any of the usual suppliers have the kits. For an even better upgrade, though at mor cost, you could also opt for a front disk conversion. They are making them now that retain the original 6 lug bolt pattern, so you can keep the stock wheels.
