Hurst offers a factory rebuild service for old shifters, you can read about it at
http://www.mrgasket.com/hurstfaq.htm
Is your shifter original equipment? On their webpage it talks a little about Hurst shifters that came as original equipment, and it says the linkage was different from aftermarket Hurst shifters. That may be the problem.
They also have a tech support telephone number you can call at 216.688.8300 ext. 5, 8:30 a.m. – 12 p.m. and 1 p.m. - 5:00 p.m. EST or fax 216.688.8306