Should be very little "emissions" systems on that vintage to tinker with.
If I remember correctly 1980 was the last year of Cat converter exemptions for gas vehicles exceeding 10K GVWR (my Dad bought a 1980 Ford 1ton pickup with 400CID engine, had no cat converter, 1981 was first year that all needed cats).
However, it was equipped with a SMOG AIR PUMP system.
I suspect your 79 Dodge most likely will or should have a smog air pump.
The smog air pump would add pressurized air into the exhaust system, this would have the effect of thinning out the emissions at the tail pipe.
A malfunction of the pump and or valves, missing /removed pump or no belt to the pump will result in higher than expected "emissions".
You also should have a EGR valve and passages which tends to clog or get stuck.
Others have mentioned carb tuning which also can affect emissions, clogged passages in the carb or incorrect setting will effect the emissions.
Most vehicles of your age, folks have removed and discarded much if not all of the "emission" related stuff, most times it failed or caused poor running conditions and not to mention killing power and mileage.
Sadly, you are on a uphill battle trying to find a old timer who knows a thing or two about proper carb tuning, doesn't take much misadjustment to mess with the emissions.
Quite frankly I am surprised that there is no exemptions for that age of vehicle. At least in PA they simply look under the hood and under the vehicle for known emissions equipment (doesn't need to work, just be in place) that belongs on it for the age in most counties that are not required testing.
