Slant 6 to 318 conversion...

What year Demon? I would make the switch to the 10.5 clutch and bellhousing with the V-8.

Brewer's Performance - Mopar A833 4-Speed Transmission and Component Specialists

You may be able to find a 67 or 68 273 or 318 bellhousing for the 9.5 clutch and your A-230 that would work.