I had the fluttering PCV problem too. I think just too much air was going through it after my rebuild. I shoved a restrictor(an old 1/4" drive socket) into the rubber line by the carb and that cured it.

1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)