Just the 4, 4A and the 250. I've seen photos of owners who fit a surrey top to their 6, but it was never offered as an option on the 6 from the factory.
As an aside, in the five months I've owned my Lotus Elise (which has a Surrey top), I have never fit the hard top since removing it the week I brought the car home. I would imagine that if my 250 with a surrey, it would always run with the soft top, or no top at all.