How wide did you open the top and 2nd rings too?
Are these new rings or the old, broken in original to this build rings
Sounds like you may have twisted a oil ring and spacer up when installing the pistons work I've never done that whistling
I would do a leak down test on the motor when cold and hot, rock the crank back and forth a little bit at TDC also scope wrench twocents

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)