I probably should have mentioned this before your swap. The Savana / Express HB Master Cylinder is "quick takeup" design. On our buses with 3 1/2 X 13 rear drums, several factors including this MC contribute to rear shoe overheating. We have gone a long way toward making the rear brakes on the '97-'02 buses last as long as they did on the 95 and down vehicles, and one experiment was using the older MC in the newer van. With the older cylinder the brakes apply quickly without the slow, lazy feeling that accompanies most quick takeup m/cyls. It requires a little more pedal effort but it's really not bad. Ultimately, anyone wh's driven for years appreciates the "direct" feeling provided by the older m/cyl.

Additionally, if your van has "auto adjust" built into the park brake pedal, this mechanism works to keep tension on the park brake cable so the brake is always in adjustment. We've found this can prevent shoes from retracting fully when the brake is released. We switched long ago to a park brake pedal from a '99 K30 truck (others may be the same). If you decide to pursue this change I can provide a few more details.

Finally, we've replaced the rear wheel cylinders with smaller diameter versions from a 3/4 ton van and tried to choose front pads that are a bit more agressive. This places more of the work to stop the vehicle on the front brakes. We get about 20k miles between pad swaps for these stop and go, in city vehicles. This may not seem optimal but a pad replacement can be done in 1/2 hr where a rear brake job including replacing drums can require 4 hrs or more.

Anyway, keep up the good work.