Delayed Disc Brake Release

I’ll try to be brief…

1970 Dart, ABS Powerbrake (Orange, CA) front disc brake upgrade kit for the original 9” Drums, 5x4” pattern.

Issue; After braking to a stop, both front brakes are slow to release (3-5 seconds) after I release the pedal. If I jack up the front end and have my wife step on the brakes, I can’t turn the wheels for a few seconds.

Supporting info;

• system normally installed and bled-I did a similar upgrade on my ‘69 Barracuda (SSBC)
• I had to grind the stock spindles for caliper clearance, they slide freely
• new hard and soft brake lines
• new disc brake master cylinder without a residual pressure valve on the front discs
• proper/stock brake cylinder push rod
• no discoloration on the rotors or appearance of an overheat situation
• This happens to both wheels

ABS is no help, really, and the only thing I can suspect is the distribution block As it’s the only thing I haven’t checked. (I swear I replaced it with a combination‘proportioning vale and distribution block)

ideas?

Thank you,