Does anyone know the diameter of the mechanical fans that came stock on the early V8 thirdgens? What other vehicles would have a fan with lots of blades that would fit the stock shroud?

I'm running an 18 inch flex fan in a stock shroud without a problem. I would guess most GM fans that are around 16-18 inch would probably fit. Make sure you get the correct rotation though( I know of someone that ran a fan backwards for quite a while--it worked ok around town).

That's what, a 7 blade fan? How well does it work for you? I've got the stock 3 blade fan that came on cars without air conditioning. It may have been adequate for a stock LG4 but with my setup now it gets hot alarmingly fast when it sits idling.

Flex-a-lite 6 blade.
http://www.flex-a-lite.com/auto/flex.htm
Works great, I can run the A/C around town in 100 degree weather and it runs 190.
model 1308

I might give one a try. Staggered blades would be nice but you can't hear a thing over my exhaust anyway. I like the sound of the 10,000 RPM rating, too many stories about flex-fans throwing blades made me kind of shy away from them.

I've had a cheapo summit fan toss a blade. Went down through the shroud (lucky). But, that might have been my fault--I bent that blade a few months previous and probably weakened it. It's quieter than my 91 Jimmy's stock fan when the clutch is kicked in.

What kind of clutch are you using with that, by the way? Might as well replace everything while I'm at it.

No clutch, aluminum spacer.