I've got a 69 with a 454 and a 4 core factory radiator. My current setup is a 19" flex fan which I can no longer stand. I want to go to a clutch fan but am concerned that I won't be able to squeeze one in. I've measured 3 1/4" from the pulley to the radiator. Is it possible to run a clutch with the OEM fan or am I going to have to run the OEM fan as a straight fan?

I don't own a Big block but on my small block, the edge of the water pump pulley to the dead center area of the shroud (where you want the fan blade, half in half out) is 1.375". My understanding is the big block shrouds are shallower so I would imagine with a clutch installed at the 1.375" point you would be within the shroud area for the fan to operate properly. My clutch is 3" total depth so it wouldn't hit the radiator but it does sound tight.
Flexalite 5255 Fan Clutch
FlexaLite 5718 18" Fan Blade
http://69camaro.nextmill.net/pics_011304/fanclutch1.jpg

Thanks for the info and the pic. I'll head to the parts store with that part number as a reference. Sounds like this may just work. I just wonder if I can buy that at a local parts store.......

Not sure, but they might! Summit is where I bought mine for very cheap and then its only like $9 shipping. Might consider the 5719 fan if you have 19" of fan clearance.