I taped into the by pass hose "see pic" had the heater core. Installed a 4" 12v fan behind the core. This setup keeps the cab 40dg warmer the the outside temp, Fan was $8, hose was $6, clamps $1.50. Hope I helped.
http://oi40.tinypic.com/1sxd1i.jpg
http://oi39.tinypic.com/2ebbcbt.jpg