When I did this conversion on my '50 with a 261 I used the stock flywheel and simply bought an 11 inch pressure plate/disc set up with 26 splines. The 11 inch pp is a tight fit with the stock bell housing but it will work. If your flywheel is drilled for a 10.4 pp that should be plenty strong enough and a less tight fit. I went with the 11 inch since my engine was warmed over and we use it for some drag racing. I'm not familiar with the 14 spline set up. The only other mod I had to make was to enlarge the 4 mounting holes in the trans case every so slightly to a full 1/2 inch hole. With that they lined right up with the bell housing bolted right up.

1964 Chevrolet C-20 Fleetside, Otis
1950 Chevy 1/2-Ton, Kirby
1950 Chevy 1/2-Ton Shortbed, Walter