Call Santana with the serial number. They are very helpful.
I recall there may have been some issues with some earlier Santanas, in the steering tube or perhaps the fork, for which they recommended a retrofit.
When I was shopping for a used Santana a few years back, I called the company regularly with serial numbers and they were happy to help. They could generally tell what year/model/size it was. They steered me away from some older models, telling me the retrofit would make it cost more than buying a newer model. They were not trying to sell me a new tandem, just wanted to help put me in a good used one.