Andy,
Push fan with a condenser in the way is not likely to get the job done.

Think puller, gotta have a shroud to help for stop and go, if you can fit a 16" something around 2200 cfm is good. You're going to lose some flow with the tight confines you've described. The shorter pump would be better, you pick up another 1 1/4", fans work better if they're about an inch away from the core, especially with the shroud.