I had a bad overflow problem once, Fuel drips down and finds way to the lowest point which is the brass nut that you had to tighten, don't know if this is so with your car or whether it's actually leaking from the tubing/connection. My problem started in 94 when they stopped selling leaded gas, somehow the needle valve inside the float chambers weren't sealing the fuel like they use to with leaded gasoline. I then did some research to find any other cause for the overflow, It seems that a lot of fuel pumps produce more pressure than the SU's can handle. I got me a fuel pressure regulator which solved the problem. LAter I bcame more adventurous, I dismantled teh fuel pump and replaced the spring inside with a softer one of the right dimensions and the problem was solved (Now the fuel pressure regulator is in storage)... Hope this helps