For the front, Menani makes repros of most of the quality 4LS fronts but they're not cheap, especially against the current US exchange rate. The least expensive is the 230mm Grimeca 4LS. Also, the Suzuki GT750 4LS is favored in the US primarily because of availability/price.
Motocicli Veloce (?) made (makes?) replacement side covers for the Grimeca that mimic the early RC Honda race brakes. A fellow in San Francisco used to make Ceriani style side covers for the Suzuki but I haven't spoken with him in years.
Interesting choice of the CB72/77 rear. I believe the CB77 may be larger. In fact, I have one I'm planning on using by flipping it left to right, repositioning the control levers, and mounting a cable guide to the brake sidecover. I'll be running it with a Suzuki front in Ceriani RR forks. Both are 36-spoke. The CB77 rear axle is the same diameter as a CB750. Please let us know the details if you get into the fitment before I do.
Rickman-Hondas didn't have cush drives either and I've never heard of anyone having a problem. Probably depends on your riding style. Good luck on your projects. RR