#187 or #699 from a C-Body. Idler may still contact the pan at the point circled below but can be massaged slightly. A #971 is supposed to work too but it doesn't have the notch. It may be more readily available (new?)
I have the 187 pan and pick up mentioned above, if you need it. also you can put 3/8" or 1/2" shims between the k frame and frame rails, will give you that amount of clearance. the factory did it on the 68 hemi superstock drag cars!-----bob