Four Speed ???

It will fit and work but it's most likely a lighter duty trans and clutch set up unless it's been changed along the way.

My 68 Dart is/was a 273/833 car and it has the lighter duty 833 with a 26 spline output and a 9.5" clutch.

I built a better 318 for it and found a 10" clutch that fits on the 9.5" flywheel, I had a local clutch shop go thru the pressure plate, they replaced all the stock springs with a stiffer units and added an extra row, it had 12 springs stock and now has 16.

I'm not sure how it would hold up with sticky tires, I'm running hard street radials and it just spins thru 3rd gear when I run it hard.