disc brake conversion idea -- need feedback

[akahige]

New member looking for some expertise. I know this has been discussed to death, but...

I've got a Dana 70 full-floating rear axle that I'm interested in converting to disc brakes. The common thing is to use front calipers on custom brackets. The hitch -- if you want to call it that -- is that I want a "real" parking brake and not something like a line lock, so that pretty much eliminates the front caliper idea. That simple demand seems to have severely limited my available options (short of just coughing up boatloads of cash for an aftermarket solution).

In looking through every truck and offroad forum I could find and there don't seem to be a huge number of options. At least that people have worked out on their own. I may have hit on a "new" solution and was hoping to impose on y'all's expertise...

A lot of MFG's over the years have used D70's in all kinds of vehicles -- especially Ford, and they put disc brakes on 'em. And that got me to thinking. D70's or not, GM has taken to putting rear discs on heavy duty axles for more than a few years now, and those axles have real parking brakes. But what I've never seen anyone talk about doing is adapting a set of full-size rear discs in place of a set of full-size drums. And I started to wonder why...

To sum up, the standard alternatives for this sort of project seem to be:
1) Skipping the parking brake altogether
2) Using late-'70's Cadillac El Dorado calipers (which have an integral, though totally unreliable parking brake mechanism)
3) Using Explorer calipers since they have an integral parking brake mechanism. (Requires that you get blank rotors and drill them for the required bolt pattern.)

One's out of the question, two seems less than ideal, and I worry that the Explorer setup in general isn't heavy duty enough to stop a loaded 3/4 ton (despite the fact that it has the p-brake feature). Which brought me to the possibility of using a full-size Chevy/GMC brake setup. I don't know enough about the big trucks -- or the newer light duty ones -- to know how many years and which parts will interchange. My assumptions are that this is the drum-style brake that mounts behind the disc assembly, and that it will mate up with a standard cable actuator.

After reaching this epiphany, I'm also assuming that there must be some really obvious reason -- obvious to everyone but me -- why no one's done (or at least discussed) this. Every time the subject seems to come up, people are recommending the really expensive aftermarket disc conversion kits (Blackbird, Currie, etc.) over what would otherwise be an infinitely cheaper stock solution. The only thing that I can conclude is that people aren't generally looking to do discs on 8-lug trucks.

Anybody got any thoughts on that?

michael


P.S. If it matters to the discussion, it's a D70 dually axle going into a '63 GMC 3/4 ton p/u.