Transmission Crossmember build advice sought

Hi, I'm new to the forum but a long time subscriber to Car Craft. I've recently come into possession of a 76' Cutlass with 20,000 original miles on it. The first problem I've had is that at least one of the freeze plugs was rotted through, which I understand is common for this car (350 ci). In order to fix the plugs - I'm replacing all of them - I had to remove the exhaust manifolds. Now it occurs to me that there really isn't any reason to put the manifolds back on when headers and dual exhaust systems are readily available. The issue now is that the 76' Cutlass has a single hump transmission crossmember that is wierdly S shaped to accommodate a catalytic converter. Finding a used 73-74 A-body crossmember is extremely difficult for obvious reasons and the aftermarket crossmembers available are expensive and seem like overkill for a car that I just want to tool around on the street.

I've come to the realization, leafing through my old issues, that a true Car Crafter would simply build himself a transmission crossmember. So, I've come here seeking advice: If you had a welder and a chopsaw,
1) what would you build your crossmember out of?
2) How do you suppose you might go about it?  

.125" wall 2x2 square tube would probably work best. I'd just put the car up on stands then make sure it's level off of the frame rails from front to back and then measure the output shaft height using the center drilled center on the output shaft for a referance point then measure to the ground just to be sure that the height remains in original location and it would be a good idea to put a degree angle gauge on the output shaft for future referance too. Then pull a measurement from one side of the frame to shaft center so you'll be able to keep everything square. Also it's not a bad idea to write down all the measurement. Good luck  
All the power in the world don't mean a thing if you can't get it to the ground!

just notch the one your crossmember, measure and mark where the exhaust pipe will have go. cut the lower side and add braceing to the top side. a piece of 3/8 thick flat stock and good welds will work.