Flexplate swap - Need help

[BITS1611]

Good Evening Everyone,

I need some help regarding a flexplate swap. I bought a 6.2L engine (running) 4 months ago, however just a couple days ago I started having issue with the starter. Starter was moving a lot when starting, I removed and re-seated the starter a couple of times, I also bought new starter bolts (just a hair fraction bigger). But soon enough the starter would not line-up with the flexplate teeth and at times the starter would fall behind and hit the flexplate. I'm pretty much frustrated at this point cause now my flexplate teeth are now rounded & smooth .
Do I have the wrong size starter?
How can I confirm this starter is the correct one?

Quick history on recent purchased engine: John got the engine 14 years ago (Engine case block #14022660), but never got to use it cause he sold the truck it was suppose to go in. John can't recall the Year/Make of truck engine came out of, John thinks it was from a 1983 truck (Chevy/GM). John said he bought the starter on amazon (Model: 6469N, Serial: ACL16L1, Volts: 12V).

My original 6.2L has a crack block (Engine case block #14022660). My question here is could I swap in my flexplate off my crack engine? Both flexplates are NOT a match.

As you can see in "Picture B" flexplate is off my cracked engine have three small holes above/or below the 3 larger circles, as to "Picture A" is off the recent purchased engine DOES NOT have any small holes above/below the larger circles.

I know this is a lot of information and hope my pictures help too.

Any help is greatly appreciated.