The ac on my 1978 hardly moves any air when the ac is on any ideas?

Hi, Do check ALL connections under the dash. Years of bumping down the road and the fuzzy foam on connections tend to fall apart and leak. Also the core is apt to be plugged with various materials from critters and falling from trees. Is the fan running? 

Yes the fan is running in all speeds just not much air coming out the vents and in South Texas that is important!

Pull the fan motor and make sure that the blower wheel is tight on the motor shaft.  Check the air intake on the psgr side to make sure that it's not plugged w/ debris.

Thank you I will check them all out!

Yes do that - check for debris in the path of the air. You will be surprised what collects in there. When I re-did the air box in the 72, I found plenty of Evergreen needles and squirrel hair clogging it up probably 75%. The previous owner parked it under a tree outside - wow what damage that did.