A mate of mine fitted one to a classic Honda and wasn't overly impressed with the braking ability initially, I think due to set up hassle to get all shoes working as they should. Care in setting up seems to be the key. If my mate's experience is a guide it's not going to be a simple bolt on replacement.
I run an RGS with a 8" single sided Goldie front brake with an Eddy Dow Duetto TLS brake assy. which is good and still looks period. If you can't get one of those then I would get a 190mm front hub and fit a TLS conversion from say Phil Pearson, the Gold Star wizard. This would give you the brakes you need and still look period. Job done!
Whatever you do, don't fit one of those 'common' Triumph type TLS brakes from later models. (I may be wrong but to fit those you need Super Rocket fork leg bottoms anyway).