Yes, return those plugs. You need all the fire you can get from the business end of the plug. Bosch still makes a W9DC without the resistor. The Autozones here in North Florida do not carry them and they don't show up in their computer system. They do carry an NGK equivalent and I used them for a short time with seemingly good results. You'll need to call around to other stores to find the Bosch plugs but they can be found, and can be bought via the internet.
Ray
'68 280SL 4-spd Coupe