I have a 1978 Ford F150 that has a modified 302 with a holley carb.and cobra?

valve covers .I inherited the truck 2 yrs. ago when my brother died.The emissions are giving me a bad time because that's not the way it came from the factory.The youngsters at the testing know nothing about mechanics and old school,not to mention modified.It's not easy trying to find an air cleaner shroud from 1978,besides the vent situation for the valve covers.I don't have $$$$ to change everything back to original.There never was a problem in the past that I know of.My brother was a mechanic for over 25 yrs.and I don't believe he would go around emissions.What do you think is the best result of the matter.It pasted last year with no problem.It past the equipment part.I'm going through this all over again this year.