I am using black urethane mounts from Energy on my wagon. Have them on my 70 El Camino and am very happy with them. Doing the same thing on the wagon. However, I am adding the bolted mount under the doors (wagons/pickups have a floating bushing here) and have gone thru the trouble to add the extra 2 bolted bushing at the fire wall for 4 total firewall bushings. Normally the cars only have 2 bolted bushings.
The El Camino kit should work, I used a Monte Carlo kit to get the 6 extra bolted bushings, and then had to get 2 extra floating bushings over the rear axle (Montes are not supposed to have these so they are not in the kit).
I bought my parts thru Summit and then was able to get the extra 2 bushings I found I needed from a site that sells them individually.
Feel free to ask any questions,