Temporary Exhaust
Option 2 about 150 with good mufflers. If you are going to run duals, just build your front pipes with mandrel bends and straight pipe and hang mufflers.
Option 3, bite the bullet and get the exhaust built.
Option 4, deal with the noise.
Oh you will need a good way to cut the tubing too, I have used a sawzall in the past, but a good bandsaw works much better.
If you do it this way, you will have to make several cuts and welds, way to many to clamp and expect to hold. You could clamp on the muffler but the rest need to be welds.
Check out my s10 build in my signature, I build my y-pipe in this manner and it probably only took 2 or 3 hours.

