Depends on the size of it really, my parents had an old 70s Monza caravan that was 4 berth but really small (about 11ft long) so towing that with a 1.8GL would be ok, but anything bigger than about 14-15ft will be too heavy.
Just look at the figures for the caravan before you buy it, the manual should say or it will be written on a panel in/on the caravan how much it weighs when loaded/unloaded.
Then going by the 85% rule I quoted below:
If for example the car is 1100kg when empty (anyone got an accurate figure for a Mk2? ) then the caravan must not weigh more than 935kg when loaded.
Curious though, your sig says you have a Mk2 16v, do you not have that, or do you not want to use the 16v for towing ?
The 16v will be better because of the power, but won't make any difference to the maximum weight you can tow.
Also personally, I wouldn't choose to tow with an older automatic because if it changes gear at the wrong moment it will be annoying (especially if it's not quick at changing), for example when driving up a hill.