Slow pedal return after rear disc.

[BR3W CITY]

Hey yall, I just finished doing a rear disc swap on my truck, but have noticed a fairly slow pedal return after a stop.

Some info;

LS swapped '66, running hydroboost from a circa 97 Astrovan, including the master. Front brakes are Wilwood D52's, and WAS running stock 70's rear drums. On this setup, truck stopped well and pedal was responsive.

Now,
Exact same setup, except swapped the rears for stock-type D52s (aka my old front brakes) using the CaptainFab brackets. Bled the brakes down, bled the hydroboost also, got a rock hard pedal with truck off.

Drove truck a bit to test my prop valve settings, and noticed a very slow pedal return. Brakes don't appear to be hanging up badly (no smoke, noise, or discoloration, and I can watch them work with removeable bed floor). I put ~40-50 miles on to see if it sorted itself out at all, and the slow return is the same across all conditions.

So; are we thinking I need a disc/disc master off of something like a 'vette? Truck stops ok but the slow return ain't great for safety and repeated stops.