I built a '67 very similar to yours, put disc brakes on the front, rebuilt the back drums and put a mid-nineties Chevy 2500 brake unit on it.

Had no trouble whatsoever since the (2004 6.0 w/4L80E) engine already had a power steering pump on it. Only had to plumb in the brake unit. The pedal linkage bolted up - had to trim down the mounting flange a little and redrill to match the truck firewall mounting bolts.

The thing stops on a dime, had no issues with sliding the rears or whatever. I have never liked the looks of that massive vacuum booster on the firewall but the hydrostatic unit is relatively small.

I put an engine cover on mine and I dont think it would have fit with a vacuum booster on the firewall without a lot of trimming.