Exhaust flange nuts and bolts, what size?

[Lee Sumpter <leesumpter@xxxxxxxxx>]

I changed the exhaust manifolds on my 64 Fury to the HP manifolds from
a 69-70 B Body. The flange on these manifolds is 3/4" thick. What is
the standard thickness of an exhaust pipe flange? I dont have anything
to go by, and want to purchase stanless steel fasteners for when I
take the car to a muffler shop to have the pipes fabricated. I am
thinking the threads should be 7/16" fine thread, but need to figure
out the lengths.
Thanks,
-- 
Lee Sumpter