Chuck,
The Jaaag project is currently in the works, though the Elan has to be finished first. As of today, the project consists of a motor, bellhousing, T5, new wire wheels, Jag diff and MGB front kingpins. The chassis is hopefully going to be cut in January (laser tube cutting), the rest will be fabricated sometime next year.
As for a bellhousing/adapter, I sent a CAD file to Xometry last week, it's supposed to ship early in January, but don't think the CAD file would be of much help for an XJ6 or XJS.
Rod