Ok thank You for explications and picture.
I actually have an aftermarket 17" 6 blades and spacer.
I want a clutch for a stock look and because during winter engine run too cold : 180-190° max (I think)
I already think that fan needs to be in the "middle" of shroud (half in). This is my configuration:
Fan placement looks fine to me. Would not move it any farther into the shroud (closer to the radiator).
Those temps in the winter would be about what I would expect/want.
"Stock look"? In 1963 (the only year I remember), engines with less than 300 hp, and engines w/o air-conditioning, were 'stock' with a 4 blade fan and no clutch. If one had either a/c, or 300 hp, GM installed the fan clutch. I think w/your 350, you could go either way and call it 'stock'. Also, the 'stock' fan w/the clutch was the 5 blade (unsymmetrical).
I was told a while back by a source I considered knowledgeable (but I've found no documentation) that the 'red' HOT light comes on at approx 240 F. I've never reached that temp on my gauge, and my 'light' has never illuminated. My max was about 225 F while sitting in highway construction traffic for close to an hour in 95 f summer temp. I was concerned but I had no where to go. The car never 'burped' out any coolant and when I was able to move, the car cooled off rapidly back to it's normal 190 'ish' F.
Again, I'm not trying to talk you out of of the fan clutch. Just trying to be helpful.