Disc brake system
I have a '77 Excella 500 31' with the vacuum hydraulic disc brakes and they are fantastic. You need a source of vacuum, I used a vacuum port off the back of my manifold on my '01 Chevy 2500hd and it has worked fine. I tied into the vacuum system going to the brake booster on my '92 Chevy z71 4X4 for the vacuum source. I then ran a in-line check valve a foot or so down the line from the manifold connection. I used airbrake hose with 3/8 fittings. I then ran the airbrake hose inside the frame all the way to the back bumper. I used a 3/8" fitting connected to a 1/2" female industrial air fitting and fabricated a mounting plate to fit it next to the 7 pole electrical trailer connection. The trailer has a 3-4' air hose with a 1/2" male industrial air fitting that plugs into the female fitting I placed under the rear bumper. It provides the vacuum necessary for the brake booster on the trailer tongue. The brake controller mounted on your dash will provide the current necessary to release the booster which will apply pressure to the hydraulic lines.
It has been an excellent system although some who don't understand it will recommend you chunk it for electrical drum brakes which are definately inferior. There are systems which will eliminate the vacuum hose from the vehicle and actually replace the entire booster system on the tongue. Andy at Inland RV has material on the system but be aware it is over $1000 best I can remember. It cost over that to have the factory convert your system over to drum brakes.
Last, do a forum search and you will find that I did a full explanation on what parts I used. I can send you a few pictures of my setup if you want.
'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