Try these Fan Clutch numbers to check online for clearances. These are very short and I probably have a whopping 1/4" to 3/8" clearance behind the 3 core radiator.
NAPA 261306 or 36944 has bushing insert.
I have used these in my 64 Max Wedge Belvedere with a factory 7 blade fan and 635 radiator. As a side note however, I ordered three fan clutches to find one that actually worked well. Amazing the performance difference between two or three new fan clutches in the box.
On another note, regarding Evans Coolant using all factory components. Has anyone used this with success keeping engine coolant where it belongs under the cap in lieu of marking its spot on a warm afternoon? After spending the bucks $$ for this coolant for a complete 100% conversion as required I found out something many of you may already be aware of. This coolant has a much lower operating pressure generally it also has a higher operating temperature. When calling Evans they confirmed this, that nobody mentioned after questioning "several" businesses and users of the product prior to my purchase. I believe operational temps with the relatively thin viscosity is probably operating approximately 30 degrees warmer. I couldn't get a straight answer from anyone at Evans as to actually how much higher operational temperatures could be expected. But with a lower pressure supposedly keeping the fluid under the radiator cap and not coating the asphalt. At some point I will remove the coolant and try 50/50 of the yellow jug or something else and see what happens.
Living in the hot state of Florida at times makes it difficult commuting in traffic. With new cores (heater and radiator), new t stat, new cap 16 lb. a very clean block interior are there any words of wisdom other than shove in a bigger radiator and electric fans when mixing horsepower and a 22" factory radiator? Unfortunately that is out of the question.