1974 F-100... straight six 240 ... C4 automatic trans.

my current issue is that i am on my 3rd starter and havent figured out my issue. majority of the time when attempting to start i will get the dreaded grinding noise. with the lower inspection plate off the tranny, its clear the flexplate is not spinning when this happens.

bought the truck a couple months ago and this started. purchased a new starter and when i went to replaced found the top bolt hole stripped and flex plate had some damaged. pulled the trans and replaced flex plate and had bolt holes re-done by local machine shop.

i also moved onto 3rd starter since bendix gear was chewed up. also replaced starter soliniod and checked battery.

still stuck with a truck that will rarely turn over properly and cant drive...

what am i missing, i feel like i have replaced everything.