I know several people who have purchased Henry Js with the intention of turning them into streed rods and then changed their minds after finding out how easy they are to maintain in original condition and how much fun they are to drive that way. If your intent is to use it as an every day car, and drive on long trips, I could understand you wanting to "modernize" it as they do not maneuver the way today's cars do. If your intent is drive it to a few shows or cruise nights, I think you'll find that leaving it original is a lot of fun too.
I, and many others, are always here to offer assistance and insights. There's a lot of Henry J knowledge that visits this board. Mechanical parts are easier to find than most people might think, especially for the four cylinder cars as the Jeeps used that same engine from the 1940s to the 1960s.
Good luck and keep us updated.