while it could probably be made to work, I think you might be better off using a latter model 3 speed and bellhousing made to fit behind the 318 (trucks Dusters and Darts are good donner vehicles).

The 3 speeds are not in high demand so the cost is generally pretty reasonable.

I kind of think the fabrication modifying shift rods/clutch linkage /crossmember would be easier and cheaper than trying to adapt the original tranny to the 318. You would also have the peace of mind in knowing the tranny would hold up behind the 318.