First up, Rusty Rat Rod has got the right idea and is dead balls accurate.
Ask Summit which one you'll need.
The cranks can be machined for a modern trans easy. Do not modify the crank to "make it work" , just use the correct flexplate. Use the 8 bolt stuff. Do not make the 6 bolt stuff work. The only part that gets attention is the pilot bushing for the manual trans. That may require machine work.