which trucks have the double hump crossmember?

[crossy]

Originally Posted by bigblock73

Eric, the early to mid 70's trucks had them, regardless of engine/suspension setups. I want to say 73-76. My '73 1/2 ton 350 equipped truck has one.

yep, they got rid of em when cats came along, thats why only heavy series trucks,over 8600lbs. had them after that, 9no emissions required).
Slonaker mentioned the taller frames. I never really saw a need for the upper piece (brace)and that is the only thing different on 3/4 or 1 tons because they are longer for the taller frame.
A Good source is dead diesel trucks and there are plenty of those around.
If the bolts are original they shoould be 7/16 diameter with a 5/8 head but i've unbolted a lot that had only the 3/8 bots with 9/16 head.