my starter was working great until the exhaust shop noticed the ears were cracked. i brought a starter from autozone and had them install, since then the starter has made a ton of noise and now slips and grinds, i can turn the motor by hand and sometimes it will start sometimes it will grind. i have removed the inspection plate and the teeth look ok none are missing. it almost looks like the starter sits too far out.

the ring gear has 184 teeth and the starter has 9 teeth.
does anyone have a suggestion on what could be causing this issue?

the exhaust shop had noted that there is no block plate between the motor and tranny.

the truck is a 76 f150 4x4 auto