You can usually just pull the coil wire off the distributor and hold it about 1/4 inch away from the head or other convenient metal surface. Just keep your hand away from the end while someone cranks it. You'd like a nice fat spark. Thin, wispy sparks are not a good sign. If they haven't been replaced in the last few years you might just get a new points-n-condensor set and put in instead of messing with the old ones. Set the points gap carefully, then reset the timing. If the spark is still weak it could be the coil. I've had several old coils gradually go bad on my various old Volvo's. They usually don't go out with a sudden failure - the spark just gets weaker gradually.