18 spline A833

Suit yourself. a 18 spline is overkill and the wrong tailshaft/shifter mounting for what you need. Check out what 18 spline pressure plates are available. A 10" clutch bellhousing/flywheel id about the biggest you can fit in a early A. Hemi's never came with a 10" clutch that I know of.

You can put a 10.5/10.95 clutch and bellhousing in an Early A with no mods to the car. Brewers Performance sells the parts.

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

I did that to my 64 Barracuda, including a 10.95 big block pressure plate and clutch.