Ranger,
Your intake can be welded...this only needs to be done if the crack would cause a vacuum leak.
Another option, and a better option I think, would be to have a automotive machine shop plug the manifold. This is done with a series of holes that are drilled, tapped and plugged with cast iron break off screws in a overlapping fashion.
Brazing the manifold would be a option too. I am not familiar with the GMC, but it sure seems strange to have a crack in this manifold, and especially in the carb base area.
I have never heard of using a belt sander to flatten a warped manifold. If the jimmy setup is like the Chevy ones, both manifolds are usually milled TOGETHER on a specific machine built to mill cylinder heads, flywheels and manifolds.
Eugene is full of machine shops...I have dealt with several of them over the years. Make sure that the intake is really cracked and needs repair and be sure the belt sander deal is going to give you the results you want.
If the manifolds bolt together, they must be flat, true AND the same depth from where they bolt together.
Stuart
