Re: FUMES INSIDE EARLY74
Common problem with the Z, especially the earlier 240's.
Check your hatch seals, the taillight seals, and all openings on the back of the car.
A lot of times, even though your seals on the hatch are there, you need to make sure that they're being compressed properly. To do this you would need to adjust the latch mechanism, don't lower the catch too much or your hatch won't align to the rear fenders.
On the taillight seals, you're not just looking at the gasket that sticks out of the back, but rather the one that is getting compressed when the light is installed. The other "skirt" seal is to seal to the back panel fascia.
Also check the openings around the fuel tank and the spare tire depression, as well as the ones on the flat portion of the rear deck.
Good Luck.