I dunno about yer 49 but on my 64, the interior always smelled like gas. When I pulled the tank out (the behind-the-seat type) I found a coupla things. First, the gasket that fits under the sender ring was cracked in several places...and a coupla the bolts were slightly loose. Second, the gas cap was of the pressurized (non-vented) type.
What I figger was happeining was as the truck sat in the the sun, the gas would heat up and pressure would try to escape thru the vent in the cap. Ooops! No vent. So it'd work its way out thru the cracks and loose bolts in the ring.
What I did was make a new gasket from a sheet of cork and re-fasten the ring. Then I drilled a small hole in the gas cap (an eco-no-no, I spose) to allow for pressure and volume changes.
No gas smells anymore...but I don't park it in the garage...there's a race car in there.
I don't think that a car or truck with a vented gas cap should stink up a garage. So I'd venture to guess that there's something leaking in your truck. You might wanna check the gas cap to see if it's the vented type...if it's not, you might be forcing gas out under pressure.
If you want to absolutely, positively eliminate all gasoline odor, you might consider a vent line on the gas tank that goes to a charcoal cannister. It could be a considerable amount of work, but who knows? It might be worth it to keep peace in the family. Btw, activated charcoal for fish tank filters works great as refill media for those cannisters.
