Carb Questions

I have a 1971 cruiser with carb issues. Stock motor and carb, spring over with 35 s. I have been told about a adapter plate that will allow 4 barrel carb to the stock 2 barrel intake. Does it exsit? Who and where? or a TBI set up. I am open for suggestions. My cruiser is mostly for off road but it will see a little road time. Help....