starter not aligning

[Angrywood]

IF this has been covered i havent found the answer i need.

i removed my starter on my 62 SBC 327 to clean it up because it wasnt engaging when the key was turned. benched tested it after cleaning up the posts on the solenoid and it was working properly.

put it back on the truck and its not engaging the flywheel properly. just makes a grinding noise and does not turn the flywheel. whats the trick on getting it aligned? i dont think i would have to shim because there were no shims when i took the starter off. what am i missing here?

ive searched the internet and most videos all discuss the shims. but like i said i dont know why i would need shims now.

thanks in advance