Battery esc combination
Peter,
You mentioned using a 320 ESC. What exactly does that refer to. "matching" an ESC to a motor refers to ensuring that the load carrying capability of the ESC is greater than the stall current of the motor(ideally). So folks simply ensure that the ESC will carry more than the max continuous current of the motor.
As far as your gel cell is concerned, looking at the PowerSonic specs for a 4.5 amp battery(just an example) it is capable of 2.73 amps for one hour. That does not sound like enough for your motor. Please remember that excessive current draw of a gel cell will significantly shorten it's life.
My suggestion is to try to determine the average current draw for you motor, "match" an ESC capable of safely handling that current, and then match a battery pack. I suspect that you will be looking at NImH or lithium to sully your needs.
Hope this help.😐