Pinging

hello all
Glad to have come across this posting, I've asked similar question about my 74 Dart
stock....
Timing is factory, 750rpm tdc....
these are Cardone (ok, ****) I've gone through 3 of them, my originals
vacuum pot went bad, traded it in, next one gave that same simptems
of not being able to acceslorate fast, engine hesitates, backfires.
traded again, then she pinged with hardly any pressure on the pedal...
traded again, then had no the backfire and hesitation again.
traded back again, now after the engine warms up, she pings at 25mph,
and she hesitates and backfires, at hard acceloration...
I know its a Dist problem, just would like conformation as to why,
is it bad Dist bearing, heating up making the Dist wobble or ?
Best
PS I'm going to a new Dist when I get from a trip I'm taking, any suggestion
this is just a daily driver,,,stock 2bbl carb 904 trans..
gets about 12 mpg in city driving...