Is the rear deraileur a Campy Gran Turismo? If so, I had one on my 1972 P-15 Paramount (with a Campy NR triple) and it shifted terribly! I would second trying a different deraileur and replacing the cables and housing if they are worn or if they are original to the bike. FWIW I am running a Shimano Crane (rebranded Letour) long cage on my Paramount and using a friction, bar-end shifter, the deraileurs have no trouble shifting through a modern 9 speed SRAM 11-32 cassette. I am using a nine speed chain as well.
EDIT: I re-read and saw it was a Rally rd. I have not used one of those but pastorbob had one on a recent build and disliked it so much ne switched it out for a Huret(?) Duopar. He was also running a Campy NR Triple.
Last edited by fender1; 10-08-08 at 07:40 PM.