Classic/Antique Car Repair: 1965 Mustang questions, fuel air mixture, mixture problem

Question
1) While driving (with the heater off and vents closed) there is warm/hot air coming in through the heater vents.  When I stop the air stops flowing.  I've put weatherstrip on the vent doors and it's still occurring.  Other than inserting a piece of foam in the heater outlet near the floor, what else can I do?  

2) There is a strong fuel/exhaust smell while driving.  The exhaust manifolds are ok/been replaced.  There are no holes in the firewall.  Is this a fuel/air mixture issue with the carbureator?  If so, how to fix?  Thanks very much.  

Answer
HI-if the heat is coming in when you are driving and not when you stop . it sounds like it is coming in from a vent ,I would check the vent switch. if it was the blower it would do it all the time.

As far as the carb. I doubt it is a mixture problem. it might be the catalytic convertor or the ex. pipes .