I would try to move engine to try to gain clearance first. Loosen motor mounts, raise engine, see if it can be nudged over or rotated. Shims between motor mounts and K frame might help. Make sure motor mounts in good shape.
Same past situation, shims etc, but still damn close, too much heat for the box was still too close to the header, Which would have eventually wiped the box out
Eventually went to a 16:1 manual box with a $200 adapter to the power column