Anybody know a good source to purchase all of the firewall grommets on a 72. Does anyone sell a complete kit?

I don't know about a complete kit, but you could try both these people. Good chance it came from Corvette Rubber if Doc Rebuild has it.

http://www.corvette-rubber.com/

http://www.docrebuild.com/dr-r-web/AAA-HOME.HTML

Ecklers has all the engine compartment grommets and they have an engine compartment seal kit. I am not sure what the seal kit includes.

They list a 4 hole grommet, 3 hole grommet, and speedo grommet seperately also.

I am told Eckler's is really nice to work with, but they appear to be the most expensive.

You may want to try Willcox. They seem to be extremely helpful and sell the same exact parts for a lot less.