Overheating at idle
I guess there is a need to be able to sit stationary for 15 minutes at near 90F? If you can't find the right pulleys at the moment, a pusher aux fan with a toggle control or a thermoswitch would help. Ignore the seller bs cfm ratings (a lot of junk on ebay) and look for the fans for the size that will fit that pull the most amps. It doesn't need to cover the whole core to be effective but bigger is better. Nylon zip rod mounting through your core will clear the engine driven fan and won't damage the core. Use the included foam tabs against the fins. No need to try and make the zips as tight as possible. They are one-time use zips.
I used a pt cruiser fan for primary cooling on a d100 with a 318 by trimming the plastic and riveting on aluminum tabs to pickup the original shroud attachment points, but not as many amps as the early taurus 3800 fan. Just showing ideas for mounting.