I own a 1980 Chevy K20 with a two year old 350 small block installed by local Chevy dealer. I bought the truck from previous owner three months ago with no interior. The truck had no heater, radio, dash or a fuse box. I am still working on the gauges. I am now having a problem with headlights and fumes in the cab. First of all, after installing new headlights I noticed that the driver side light is brighter then the passenger side. I checked all grounds and I know that all the wires are good because they're new. Second, the truck has a true dual exhaust and factory exhaust manifolds with exit behind the rear tires. Why or how I am I getting exhaust fumes in the cab? I don't have any holes in my floor or the firewall. I noticed the fumes getting stronger after I installed the heater two weeks ago. (That's right; I've been driving with no heat for the last two months) Does anybody have any ideas on how to fix these problems?