I'm searching this morning more info on the web about big tank on first generation Z/28
Big Tank this is not a RPO but a Special Service Parts
3938924 Fuel Tank (37 gallon, fuel cell type)
Heavy Duty Part List 
And Smokey Yunick testing a 67 or 68 Z/28 with a cross ram and
big tank for speed records at Bonneville.
Smokey 1
Stories
