31 Buick bumper bolts source

[Str8-8-Dave]

Anyone know where I can buy either stainless or chrome 1/2" 13 thread per inch x 7" long carriage bolts or honest to goodness bumper bolts with 6" long un-threaded bodies and 1" thread at the end?  I've tried Bolt Depot and McMaster Carr and even though the McMaster catalog says they are only threaded 1" the bolts I got had 5-1/2" of thread.  I will use them if I cant find anything else but correct bumper bolts would only have 1" of thread on the end, rest is straight unthreaded shank.   Any leads highly appreciated.