Well I have worked a fellow who was using an old Drake line TX/RX radio on PSK31. It was noticably drifting during the contact but not as bad as I would have thought. On psk31 mode it only takes 10 Hz/min drift to cause loss of communications with some programs. A mode like Hellschreiber (Feld Hell) would be far less effected by drift. Sound card RTTY might be an option as well... Generally, older tube rigs will become stable after a period of warm-up if the VFO components are still in good condition. You might monitor WWV in CW mode and listen to hear if you detect any drift over a 5 minute period.
See you on the digi bands. http://home.teleport.com/~nb6z/