When using an electric fan, it is useful to slow road air to flow through the radiator when at speed, makeing holes in the shroud that are closed by a flap when the fan comes on allow road air to pass through but close up when the fan comes on to suck all air through the shroud. VW etc. use these.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
