Sitting at idle with a non-working fan clutch will certainly make temperatures climb especially with the AC running you have double the heat issues in the radiator area between the radiator and the condenser for the AC. I'd bet your fan clutch is shot, the one on my 88 Bronco 2 was and no matter what I did it would run way too hot for my liking, a replacement fan clutch problem solved, it will idle all day long with the AC on and never get hot. Now, if you are parked but you have the transmission in gear its still going to get hot regardless. I'd start with replacing that fan clutch, all those little tricks if it spins freely by hand its bad doesn't necessarily mean anything...they're cheap, replace it, and I'm sure since you just replaced the engine in recent years you know an engine isn't cheap, so replace the fan clutch and I'd go with an HD one, yeah you'll get a lot more fan clutch noise and engagements but I'd deal with the noise over an overheated/damaged engine as a result of not having a working fan clutch. Other's have mentioned going electric fans, that would definitely be something to look into if you do a lot of idling, those fans if you wire them in correctly you could install a manual over-ride switch so you can manually turn them on regardless of temperatures for max cooling when parked...it will also significantly make your AC cool better too.