Why not just install the replacement and see if the problem goes away? I know that smacks of "throwing parts at the problem," but your car is 20 years old and there's a decent chance there is some internal leakage (insulation breakdown).

Not knowing the exact nature of your intermittent ignition failure, I'll just suggest a couple of basic things which you may have already covered: (1) in a dark garage, or (better, safer) at night - pop the hood and see if you have little blue arcs dancing over any part of the coil or plug/distributor wires. Coils can crack or develop carbon tracks which provide better paths to ground than the spark plugs. (2) Disconnect the coil wire from the distributor cap and lay the connector next to the firewall or hood hinge. Crank the engine briefly and verify you get a good strong spark. (3) Moisture such as from rainy weather or even condensation at night can create shorts to ground. Make sure your plug wires are less than 2-3 years/50K miles old, your distributor cap is not cracked, and that the 12v wire to your coil is intact and the connector is clean and bright where it makes contact.

Good luck... when you find the culprit, remember to post your findings!