Screwup after screwup... what to do?

I'm frantically trying to get my Duster back together as quickly as possible before school starts next week and I keep running into issues. I swapped the 318 for a built 360 and hit a snag with the exhaust manifolds. I got a big-outlet Dakota manifold for the right side and an old '68-70 340 manifold for the left. I thought I got a good deal because the 340 piece was brazed up at some point to fix a crack on the outlet neck. Well as I went to bolt it up the extra material hit the head and prevented it from seating. I spent hours grinding away material till it fit, only to find I broke through to the crack:banghead::banghead::banghead::violent1::violent1::violent1:. I made the mistake of putting a thin layer of JB-Weld over the crack because I thought it might hold together temporarily but just read that it will most likely boil/burn off and make a mess.:tard:

Here's the problem... I need a fix that will let the car drive on the highway to where I live an hour away. Looking on eBay there's a '72-74 manifold for $200 but I really don't feel like spending that much unless there's no reasonably effective 'band-aid'; any of you guys know of another place to find manifolds? I found a high-temp alternative to JB called "Thermosteel", anybody used this before? Once I get it up there I will bring it into the lab on campus and see if it can be welded or at worst case get some headers.