i posted on this very same thing about a week ago. the post was in the "general" topics section of the forums. also you can do a search under "gas tank replacement"
as stated you can get the brackets from a dealer for about $100 for the pair. HOWEVER these basic brackets do not have the hardware attachments to accommodate the plastic shield and do not have the welded blind nuts attached. i found a vendor in new Hampshire who had the plain brackets with straps for about $90, he also had the ones that accommodate the plastic cover but they were double the cost, i do not think those are still available from the dealer. your best bet is to try and find a good original used pair.
i got mine from a 73-87 truck guy who had a lot of extra used parts. let me know if you you need some contact info.