Chrysler produced some manual transmission Fuselage-bodied 4-speed cars, but they're really, really rare - so the conversion parts would also be really, really rare.

Your best bet may be to try the guys over at cbodydrydock.com . They're C-Body nuts and would know more specific info. Sounds like a fun project, I know I miss my '69 300 a LOT! It now resides somewhere in Finland... bawling

Good Luck! up