Many people changed out the "troublesome" Holley 4160s for Carter AVS, back then. Troublesome? The quality of the bowl gaskets and such were poor for Holleys of that vintage, so the AVS was the preferred "go to" replacement. Put them on, adjust them, and they would "run forever", whereas the Holleys needed a rebuild every year. Newer Holleys I've had did not have those issues. BTAIM
Additionally, "back-fires" and "spit-backs" through the carburetor have been know to ruin a Holley power valve, which will put the carb "on the power mixture" at all times. Another known issue with Holley 4bbls.
The Cardone brand has its quality control issues, by observati0on and the experiences of others in here.
@halifaxhops is a member in here and specializes in distributors, their maintenance and rebuilds. IF I read things correctly, you replaced an electronic unit with a points unit? If so, then the next issue would be if the rubbing block on the points was lubricated when they were installed? As it used to run well, the unlubricated rubbing block (or a so-so brand of points), would cause the rubbing block to wear quickly and change the point adjustment, after several months of use. Which will THEN also change the base ignition timing, without moving the distributor body.
As to setting the timing, DO unplug and plug the vac advance line to the distributor to set the base timing. THEN rev the motor to see if the mechanical advance is working. Taking it to 4000rpm will be high enough to check for the max advance of the distributor + base timing. No need to adjust anything for that, for your purposes. IF you check the 4000rpm total advance with the vac advance hooked up and working, the total advance can be over 50 degrees BTDC, which is normal, but if you adjust it back to 38 degrees BTDC at that speed, then the base timing will be too low. So use only the base + mechanical (vac advance unplugged and plugged) to look at the total timing for the distributor you have. THEN recheck the base initial timing when done, THEN unplugging the vac advance line and reconnecting it back onto the distributor.
The problem with rebuilt distributors is that they are "will work" for the engine they are installed into. The factory specs go out the window, by observation. You get a more generic advance set-up than the OEM-model-specific set-up the factory distributor came with. The Mopar Perf electronic ignition distributors have a quicker advance curve, all in by 2000rpm, to help with drag racing performance, which is fine for the street use.
Hope y'all get things figured out,veryone gose tote local parts store & buys a reman)
CBODY67