MG Car Repair: MGB fuel sending wiring, no screws, loose wires

Question
I messed up and did not write down the wiring set up when I replaced my 1975 MGB two post sending unit and need some help. I have two different size posts and have been able to hook up the larger post to the black/green wire from the harness. The other post I assume is a ground that I must have misplaced as I do not see another loose wires available under the vehicle. I can make a ground wire but need to know where it should be grounded to. I read that somehow it is to be grounded to the unit itself but this unit is secured by a lock ring and has no screws to attach a wire to. Is a body ground ok? It does not seem logical to me to ground to the unit when the post itself is part of the unit. Help! I have learned a lesson andin the future I will take pictures before removing parts and then later trying to replace them.

Answer
Gerard:
You are right - the green and black wire goes to the sending unit. The other wire is or should be black and is a ground connection. It goes to a common ground connection in the harness, with other 2 or 3 black wires going into it (rubber connector). If you don't find it any ground on the frame will also work- the closer to the sending unit the better. Hope this helps.