On top of what Mike said
Window rattle easy fix datsunparts.com window run channel
Rough ride... Your springs were cut. you are riding on bump stops. or your shocks are shot, bad joints
Back fire is many times debris in the fuel system, exhaust leak pulling in air, slightly improper timing or a lean carb
Smell points to exhaust leak
I would swap the rear gears to 3.7 from a roadster. You are lucky you've got a h190 pretty easy swap and it can happen in a couple hours.
I'd be more than happy to poke at your car. I am just over the bridge from you.
Brian