Which fan clutch should I run???

It's been my experience that the standard fan clutch will not spin the heavier 7 blade fan fast enough at low speed or idle therefore your car will get hot at idle. The HD one works great with the 7 blade fan on my cars. Idle 90*+ with the A/C on and does not heat up at all. I can't comment on the clearence issue though as I have E-Bodies.