Crossover was a *****. Broke a bolt off in the rear manifold (no matter how much PB Blaster I put on it). Finally drilled it out and ran my own bolts/nuts/washers to keep the issue from happening again. If worst comes to worst I just dremel through the bolt and the nut/washer will fall off the back.
My improvised but very sturdy solution:
Stainless hardware with anti-seize so no more problems. Should've come like this from the factory, but I guess their way was cheaper.