i need help with my 86 prelude!!

one of the carburetors is flooding out. i don't know if i should replace it or just the gasket....but i really don't know which one it is either.....and also could i put an si motor in my car???.....

Yeah, an 86 Si engine will work. The mounts might be a little different, and of course the wiring for fuel injection, but besides that it'll be fine. Our family has an 86 Si among others and its a fun beater car.