[GEARDRIVEN]

All if the posters have given great insight.
I recommend the suggestion by Paul in regards to performing battery cable voltage drops.
I have worked in the auto repair field since 1972 and in the GM dealer service departments since 1982.
Testing for voltage drops in the cranking system is a fundamental step and you could imagine what defective battery cable can do to the newer electronic-laden vehicles.
I am in agreement that the wiring in the starting/cranking system should be confirmed good first along with testing of the components therafter.
Also the age is the wiring itself or where repairs have been made need consideration.
I am an old-timer now, but I learned the performance life as an owner of a few....
70 T/A R/AIII 4spd blue/white
'71 T/A 455HO auto white/blue
'74 Formula 350 4spd zzzzzzzz(snore)
'76 T/A 455 4spd white/
Also a 10.0 AMC prepped '71 401 Hornet
S/C (Loved telling the Hemi guys my Mom has a Rambler that I think is pretty fast.......
Good Luck with the starting concern.....a lot of knowledge here for you to use.