Guys, I love the disc brakes on my '77 Excella 500. I've had the trailer for 3 yrs. and travelled close to 2000 miles with no problems. The vacuum hose arrangement that can be tapped into the engine manifold of a gas engine can be replaced with a Delco vacuum pump as a source and mounted on the tongue.
There is a source of parts that allows you to replace the entire booster system on the tongue of the trailer with a small vacuum pump/hydraulic unit that is connected directly to the hydraulic line of the trailer. I've seen a number of ways to do it. I'd rather do it that way than to go to electric drum brakes which definately are not superior to the disc brakes.
'01 2500hd ext. cab, 8.1 litre gas, 5 sp. Allison auto
3.73 rear end
Mag-Hytec rear diff cover
Amsoil Dual by-pass oil filtration system
Amsoil synthetics all around
265 watt AM Solar, Inc. system