Possible to retrofit a variable speed fan

[crosstalk]

Hello.  I have an American Standard single stage gas furnace model AUX040C924D3.  My basement is somewhat cold, but running the furnace fan continuously improves the temperature difference in the basement.  Unfortunately it's going to be expensive to run this fan all the time.  Is there a way to modify the furnace fan (or retrofit it) to be variable speed to save energy when running continuously? I would like it to run slowly when the furnace is not heating/cooling to circulate the air.

[applianceman18007260692]

What about installing a duct booster?

 Tjernlund Retail Store

[ACtechGUY]

The only variable speed motor available as a retrofit is a GE Evergreen motor.

http://www.thedealertoolbox.com/evergreen.php

I have been considering getting this motor, But the price is a little steep compared to the possible energy savings.

[crosstalk]

The evergreen IM motor looks interesting.  How much does it cost?  I can't seem to find any prices or anybody selling them online.

[ACtechGUY]

The price I was quoted (wholesale price) was around $300