My old (2000) Fedders isn't a heat pump, only an A/C. I have a separate LP gas heater which I never use (I bought an electric ceramic heater). The RT guys said that they modified the Fedders in 2 ways prior to installation: (1) added rubber clamps to give extra support to the compressor so it doesn't bounce around and stress the joints in the freon pipes, and (2) added a hard start condenser.
KMB1966 -- thanks for the tip on Kenmore. I'll look into that brand for size. I bought an LG that will fit, but it is only 6000 btu. I haven't opened it up or voided the warranty yet, so I can return it to Home Depot if the Kenmore is still available.