I just finished doing an aftermarket carb swap on my 82 express. I'm running a dellorto sha 15.15 with a 58 main jet and oil injection inlet which has been working great after replacing factory line, auto choke bypassed, stock throttle cable, and a malossi adapter plate. You could go with the lil shorty intake($40) and dellorto($67 oil injection version) for a plug an play experience or file down a malossi intake for tomos bikes($17). All parts were from treats, make sure to pick up a jet kit and maybe another throttle cable just in case.
*Dellorto sha 15.15 oil injection:https://www.treatland.tv/dellorto-*SHA-15-15-carburetor-with-oil-injection-p/sha-oil-inject-726185-or-2013.htm
*Malossi intake adapter:https://www.treatland.tv/motobecane-15mm-SHA-dellorto-intake-p/av7-sha-intake-022066b.htm
*Lil shorty intake adapter:https://www.treatland.tv/MLM-honda-express-15mm-SHA-intake-lil-SHORTY-p/motion-left-intake-324.htm
*1mm shim so carb fits on adapter:https://www.treatland.tv/dellorto-PHBG-1mm-carburetor-shim-p/dellorto-phbg-shim-1140700-62.htm