First off, the 2 day deadline is toast. 2 days is convenient, this is all.
Furnace cement is pretty gritty. Muffler glue is the same thing minus the grit.
I love muffler cement for small repairs, 2 bucks, Napa parts! Wet scrub with a wire brush and water first until its clean.
I have some on my woodstove for years now. I use furnace cement inside on the firebrick.
They both are basically sodium silicate, IE: water glass.
But... Junkyard Dude! What are you thinking? This is no classic that is going to be kept for another 2 decades. A 1/2 decent junker and you are good to go until he is tired of the car.
Your worst problem is the bolts. They are guaranteed to be screwed.
Without a torch you better be real good welding nuts onto snapped bolts and quick spin them out while they are still red, or easy outs.
Try soaking all the bolts in penetrating oil now, while you are planning the repair. The more you can stall and keep squirting those bolts, the easier it'll be.
I soaked my Pacer 3 days straight, 3 times a day, in Kroil and they all came out in one piece.