finding an aftermarket elecrtical fan

I have a 1982 c10 with a mildly built 350, I am looking to squeeze a little more gas milage out of it and am trying to find an electric cooling fan to replace the old clutch fan, I don't have the vehicle where I can measure the fan at the moment but am pretty sure it is either 17" or 18", and what I am wondering is if anyone knows the CFM that one of those clutch fans will pull between 2000 and 4000 RPM, so I can figure the CFM range that the electric fan needs to be, (the one I found that is recommended is a dual 13.5" fan setup but it is about 400.00 which is a little out of the price range for me).
My P/U also has a little electrical problem in the guage panel what happens is that when you turn the headlight switch as if you were turning on the interior lights it kills all the gauges in the gauge panel and as soon as you turn off the interior lights the gauges come back on. (wondering if anyone has seen this before, I am going to try to find the problem sometime next week):banghead:

My dad's '81 had the same issue with the headlight switch. A new switch fixed his. As far as the fan, mild small blocks need at least 2500 CFM, more if you run A/C or run uncoated headers. Most of the units I've seen recommended pull 4000+ CFM. Don't be so concerned with the size but with the volume. Different designs in the same size pull vastly different amounts of air. And yes, you'll shell out a good $400 plus for a good unit with a thermostat switch.

one name on an aftermarket electric radiator fan... SPAL

Your light switch needs replacing before it shorts out or doesn't work at all....replacing it would cure your problem as it also does the interior lights and the dashlights as well. If you're ever going down the road and your headlights go out, its the dimmer switch that needs replacing.