That gas smell... any suggestions?

First, you have to narrow down the "smell".

Raw gasoline has it's own smell. If it is raw gas, it can be coming from lots of places - the fuel system runs the length of the vehicle.

Combustion, or exhaust gasses smell like what comes out of the tailpipe.

Then there is the "old car smell" that comes from warming up 45 years worth of oil, grime, spilled fuel, etc. Sort of smells like well used motor oil - the vapor coming out of the breather smell.

I have a '65 Barracuda, and there are plenty of places for the outside smells to get inside. A good seal up can be done.

The trunk seal has been mentioned, but there are other ways for smells to get in to the trunk. Pull the mat out of the trunk, and put your drop lite under the back of the car at night. Have a look inside the trunk.

Anything that gets in the trunk gets in the passenger compartment. The fold down panel does not seal, the defroster hole is wide open, etc.

Smells from under the hood can come in through the end of the steering column tube, or any firewall penetration that is unsealed - like a missing speedometer cable grommet.

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