How do you tell what liter your Slant 6 is?

If you can, a clutch fan is the way to go. Eliminate all that wasted mechanical drag and noise.

You probably need to run a slim - short clutch:

http://www.summitracing.com/parts/HDA-2765/

Folks use these when putting a big block in an a-body because they fit the shaft - holes and are short

I dont know if this will work with a slant in an abody but I bet others here will know.