What bellhousing do I need?

No matter which one he uses, he still needs to make sure the crank is drilled, or he will not have clearance for the input shaft; or will need to have the input shortened.
I've never seen a 'teener of that era without the pilot hole drilled, they just don't finish sizing them for the press-fit style bushing, if it's destined for an auto trans. I had to turn the OD down on the bushings for both 'teeners I put in the Thunderbooger, in the '80's, the convienence of the non-existant Magnum eng. brg. wasn't an option.