There is a lot to be said for bringing back the "rough" I had the same issue with my project. Started out with a mild pre-war Go-Job style chassis. Planned on a roadster body but when a rough truck body came along it fell into place. There is a lot to be said for leaving it rusty, I've had a blast tearing down the dirt roads and not worrying about paint, build to suit. Even getting a larger crowd (which isn't my thing) at the cruise nights than the high dollar show guys.
I've built a few and take some time and plan before you build - that is if you go the later engine route there is a lot of issues to resolve and some money to spend, and safety is a must issue. If you go OHV V8 you'll need to box the frame, update suspension for not only the weight but torque, also steering, stopping rear end, M/C all those issues plus the space. Ford is a long block, cutting the tank and firewall, column mount all that starts to add up.
Don't rule out the flatty - If your wanting to go Ford and faster you might check the HAMB for references to the Bishop Tardel book, or search A-V8. Running a flathead will get you as much go but much more traditional without all the headache. You'll find most parts are easy to swap in and find fairly inexpensive.
700RPM - I'd love to get a copy if you scan the article.