Shims in the bell may be what needs to happen.Or get the bearing mount flange surfaced down.
Not sure how much can be machined off, but you can also machine the flywheel .015 to get the same amount.There are several places to gain some clearance. Just need to decide where to take it as to whats available to you readily.
If you shim the bell you should use a shim that outlines the botl pattern on the bell for strength. Kind of like fords shim plate between engine and trans.
Fact is stranger than Fiction