you are correct sir
a motor doesnt know,
and a plug only knows to fire when it told to fire
but its all up
to the plug maker ,, who ever that is
to have the best in house design, quality control
being i sell plugs , use plugs , race plugs,
i will always recomend what the vehicles sparkplug,
by their recomendations ,
altho youre car motor is prob nothin as to what mother mopar ever intended to have from factory
so as a factory standpoint champion was the factory plug
of choice ,
as for slapper bars what ever, if you dont know how to fix that
issue then run a slapper bar they work for what they intended
to do ,stop leaf spring rap up, or the lack of coil spring load
as for a power glide , if you have the monie to make em go
and the car lite enough go for it
as for 9 inch let all the ford guys have them !!
stick with my 8 3/4 or my dana 60