Is there a suitable replacement for a GE motor 5KCP39PGP932AS 3/4HP 12amp 115v 1075RPM 4SPD? The only one I can find on line cost 316 dollars.

I want to but and install myself

Try a local motor repair shop they usually have new motors also. Try Grainger if you have one located close to your home. Try a local HVAC wholesale supply house. Whatever you do make sure you get a new capacitor that matches the new motor you get. You never replace the motor without also replacing the capacitor.

You can use a 3 speed

NEW 3/4 HP 3-Spd Central Air Blower Electric Motor 115V - eBay (item 270388108511 end time Feb-03-10 11:26:40 PST) (http://cgi.ebay.com/NEW-3-4-HP-3-Spd-Central-Air-Blower-Electric-Motor-115V_W0QQitemZ270388108511QQcmdZViewItemQQptZLH_De faultDomain_0?hash=item3ef4631cdf)

NEW Furnace A O Smith BLOWER MOTOR 3/4 HP, 115 volt - eBay (item 260273758345 end time Feb-02-10 06:23:40 PST) (http://cgi.ebay.com/NEW-Furnace-A-O-Smith-BLOWER-MOTOR-3-4-HP-115-volt_W0QQitemZ260273758345QQcmdZViewItemQQptZLH_De faultDomain_0?hash=item3c99866089)

Now you might freeze to death waiting for an item shipped from a eBay seller. Remember to make sure the motor you get can be reversed since you probably do not know the rotation and if the air does not move well you will have to reverse the motors rotation. Just because you have a 4 speed motor does not mean you cannot use a 3 speed motor. Most furnaces only use 2 of the speeds to start with. Make sure you follow the wiring on the label of the new motor and write it down since you cannot see the label after it is installed.