If you are asking will it be enough to get you up on one cycle from aired out to ride height, I will have to say maybe, maybe not.
It might be enough volume, if you have a compressor that can pump enough psi. If your compressor cuts off at a low psi, then it probably won't have enough volume to re-fill the bags.
If you don't mind having two tanks, add another 3 gallon. If you just want one tank, sell the 3 gallon, and get a 5 gallon instead.
Even with two 5 gallon tanks, my system cycles every other time on my 77...
