Going Powerglide

Hello, I am going to a powerglide in my Dart. It's is getting a JW Bell so It will bolt up nicely, however I am also installing a mid plate (1/4") which requires a crank spacer and the Chevy flex plate which also requires a crank spacer. Has anyone tackled this before, and if so what length flex plate bolts you used or any other pointers you can give me before I begin this swap.