I don’t think I will be able to find a pair of original front blocks
Tried Private messaging you but received no reply.
The rules here state.... No buying & Selling of parts in the forums..... but trading parts with no $ involved should be no problems.
Before you start hacking & drilling & forcing incompatible parts to fit improper applications....I can fix you up with the correct Chevy brackets & will take your GMC brackets in trade..... No financial gain on either side.
Would rather take care of this in Private Messages but it seems I have received no replies & don't even know if the messages are going through.
PM for more info.