Temporary exhaust system
Well, this is my take, and I'm guessing the exhaust manifolds will take a hike later.
Get the headers you want or spend cheaply on a set. Skip the X and H pipe and just run 2-1/2 pipe and a muffler. At the end, use 2 90* bent pipes to route the exhaust from under the car out infront of the rear wheels.
If you plan on keeping the exhaust manifolds, purchase some head pipes from a source like tti. Just the head pipes. Then do like what I said above.
That is the cheapest temp. exhaust I can think of.