The Escalade rear diff won't directly work in your Silverado, because the suspension is different. The one in your Silverado uses leaf springs while the Escalade uses coil springs. The Hydroboost system for the brakes does not make a difference. That's because the power source is the only thing which changes, not the brakes themselves. You could easily change from one to the other by changing out the vacuum canister with the Hydroboost, or vice-versa. I've considered doing the work on my old Silverado, because I like how the Hydroboost works.
If you wanted to, you could use the rear end off of the Escalade, however, you'd have to do a LOT of conversion to make it work (ie: perches and connections). I feel you are looking for a direct fit, which you'd not get with the Escalade rear.
As long as you get a rear end from a Silverado or GMC Sierra with the right gears and disk brakes, you'll be in good shape. They should be plentiful as I see them for sale all the time on CraigsList and other places. I believe the years which would work range from 2000-2007 (these should work for sure, though there might be more years which would work, also).
