There are a few things to be aware of.
The first and most important being that you DO NOT USE an original type windowed flex plate.
The OEM flex plates of a later vintage had three triangular windows (not the more common round ones).
These were fitted to smaller balled motors and will fail, when and if used on the bigger 472 and 500s
What you want is a solid replacement like the puked one in your photo.
That may well seem counterintuitive, since that one failed, but that just says it was either defective
and/or implies that maybe you have an additional issue going on that needs addressed.
I would suggest that you double and triple check to confirm that your timing is not overly advanced.
Can't offer you a part number (it wouldn't help at this point, anyway), but what you want is one to fit a '68-'76 472 or 500.
Additionally, a '76-'80 425 will work
IF it fits the above described profile (most will not).
Your luck appears better than mine was when I needed one last because they have become difficult to source.
What you are after is one of these:
Caddy BB Flexplate
Not meaning to necessarily promote these guys, they just had what I was trying to find a picture of.
Alternatively, If you are industrious, the big block Chevy bolt pattern only differs by one hole so it is quite possible to weld that one hole up and re-drill it to match the Caddy pattern you need. For my time and money, I'd be inclined to pay those guys' proud price for what they have (unless you have displaced Chevy bb flex plate that fits the above profile).
Again, check your timing. Is it likely to far advanced.
You want no more than 32 at balls out, and may well find there is little gain beyond 30.
(will depend specifically on what exactly you have and are working with)
