Many 300s did have a C6 behind them so it shouldn't be too hard to do. You will have to figure out a driveline, depending on whether you get a tranny with a bolted on yoke or a slip yoke. You will also have to build a shifter bracket for the T-case.
Personally I prefer a C4 on the smaller engines. There is much less parasitic power loss. I have read that a C6 can gobble as much as 60 horsepower and some guys claim even more.
Since it won't be stock anyway, why not just get the whole drivetrain from something in the 80s and use an AOD with a married 208. It would be much cleaner, you'd have overdrive and no middle driveshaft to fool with. Or even an early 80s would have a C6 and probably a 208 but possible a 205