I bot this TA in the dreaded c0vid days and the non-original 455 seized on my way home.
long story off topic...
Anyway, it was going to take $$$ and way too much time to get it rebuilt so after a couple months of searching I found a used 455 a few states over and rolled the dice on it. Looking back it was such a risky move but ended up working out in the end.
I spent a lot of time researching before that and Len was the cheapest/best rep I could find on the internets - not that close but another option for you:
http://www.lenwilliamsautomachine.co...ong_Block.html
Good luck with your Pontiac!