I had a '67 conv, white top. The best advice I can offer is to keep it clean & dry. When not "going topless", keep the top up so the fabric won't develope wrinkles/creases. For normal cleaning, I just used regular car wash soap on the top when I washed the car. Then just let it air dry. If it gets stained from mildew, I used Comet cleanser & a scrub brush -BUT- you must be very careful not to let that strong cleanser get on the painted surfaces as it has a bleach content. Keep a water hose flowing to provide a constant rinsing. The previously mentioned workshop probably has some good suggestions/methods.
Neil Hoppe