I would like to share my experience on this topic. I have a 66 that I built a brand new motor for. Everything was new except heads and intake. The radiator was a aluminum griffin 15 x 30. Tried two 12" electric fans with no shroud. Motor would run 180-190 down the highway and climb to 220 at a light. Took the the electric fans of and tried a 15" flex fan still without a shroud. No change. Then I tried a 19x26 aluminum triple pass (no shroud) from a dirt track buddy. Still no change. Then I took the thermostat housing off to change the thermostat and to my surprise there wasn't one. The intake was from a friend that had it on his 406 in a 70 camaro. Put a 160 in it and it helped a lot. Temp climbs while sitting still but slower. I tried the electric fans again and that was a mistake. Temp acted the same as before the thermostat install. I then bought a do it yourself shroud with a 15" afco mechanical fan. That was well worth the money. Temp stays right around 200 at lights and drops down to 180 on hwy. (put a 180 thermostat) I am tempted to try a electric with the shroud but the reliability of a mechanical keeps me from doing so. I don't have anything against electric. They wouldn't put them on most new cars if they didn't work. I'm not an expert but I belive from my experience that shrouds restrictors in the coolant are a must but may not be needed for other people's setup.