65 kg is a lot of payload. Accelerating at 1.5 ft/s/s is a fair bit of thrust (evel though it's "only" 1/20th of a g, if I can do unit conversions in my head.) You will need strong motors to achieve that level of acceleration.
Also note that typical motors run in the thousands of rpm, and don't have a lot of torque, but use gear boxes to trade rpm for torque. Thus, a 12V motor with 1,000 kV constant and 2 ozin of torque would run at 12,000 rpm at 12 V; use a 500:1 gearbox and it gets to 24 rpm and has 1,000 ozin of torque! (That motor would be too small for your design case, but that's a pretty small RC car motor I described...)