That gas smell... any suggestions?

My '65 Barracuda project had a rusted out exhaust system with holes all up and down the pipes... Everytime I drove it I would get a lot of gas fumes coming into the car, sometimes so bad I would get a headache.

I decided not just for the sake of fixing up my car, but also for my health it was time for a new exhaust system. Shopped around and found a guy that does mandrel bent systems... Went ahead and put a dual magnaflow exhaust system on it that exits all the way out back... it sounds freakin awesome now. Huge improvement in power and sound, and there's a lot less fumes coming in the car... But there's still some fumes. I'm still smelling like gas when I get out the car after a 20 min drive.

I know it could be a symptom of driving an old car with no catalytic converters, but seems like there might be some coming thru the vents possibly. To cut this short, do you guys all deal with a gas smell after driving your old mopars or is there something definitely wrong that I should fix?