Here is a great example for bracing [somebody provided it in your other post in the truck forum] - it even includes the ability to dial in the gaps when doing the welding.
http://67-72chevytrucks.com/vboard/s...8&postcount=54
http://67-72chevytrucks.com/vboard/s...1&postcount=55
http://67-72chevytrucks.com/vboard/s...4&postcount=64
How bad is the rust on the body? Have any more pix?