I know that vacuum controls where the air is directed as far as the defrost, or vents, or floor correct? I don’t know how the system works but here’* what’* happening. When I give the car gas to accelerate, the a/c starts blowing out of the floor vents, when I let off the gas or reach a speed where I’m not pushing the pedal very much, it returns to blowing out the vents on the dash. What’* causing this and what do I do to fix it? Thank you for any help!

Which engine N/A or */C? Either way you are losing vacuum under load. You could plumb in a vacuum reservoir to help during high load conditions. I thought maybe you had one but it don't. I thought maybe the tank cracked. Other places you can lose vacuum are in any of the lines, brake booster or even the controller/actuators etc.

Check for vacuum leaks, and for vacuum check valves that may have gone bad.

I guess I just have to search around everywhere to find a leak huh?

Look/listen for hissing while it is idling. You can smoke test it too, but that'* more involved. I've found some crazy vacuum leaks just by tracing and looking for stuff that'* out of place, cracked, and disconnected.

For the hvac or is there any vacuum lines in the car at all? It has manual controls by the way, not digital climate control

I am not familiar with your system, but it should be vacuum controlled, with vacuum control valves, blend door actuators, etc...
Most likely the controls at the head unit have a hose going through the firewall to connect to a vacuum source under the hood, I am not sure how to find it without your cars service manual..
But you are on the right track, the issue is most likely vacuum related.

If you cannot find where your vac lines run, and inspect for any leaks, if possible inspect the actuators that open and close the vents, the arms on them are known to break...
The one that controls the front vents is located directly above the gas pedal, straight up towards the windshield. Its a pain to get your head under to see it, but I would check this.

Looks like the 88 only had the N/A engine. Plumb a tank into it.