Here is the dal on rebuilt mass air flow sensors....assuming you have a 1986-1987 we actually get the originals rebuilt by Cardone as we supply the correct original cores. If you go to any auto store in the US 99% of the time the rebuilt unit you get back will not be the factory appearing unit but the Camaro 6 cylinder one where the electric plug faces towards the passenger side instead of downward like the original. It will also have new pegs on it so you can attach your 2 10mm screws to the air cleaner assembly.
We have the correct ones and we allow for your core.. Others may have it also, but now that you know the situation you can ask where ever you go what they offer.
I've tried a MicroTec MAF. It was garbage. My car leaned out at 10psi because the MicroTec pegged WAAAAAY under 255 grams......and they are a venturi style (restrictive) sensor. Garbage I tell ya'.
from a stock set up stand point over the years we have looked at probably almost every aftermarket version even had Richard Clark flow test them with poor results. The problem is keeping stock of original cores to keep the cycle going. So far we have been lucky in that regard.