Two pushers should work just fine. I'd do the following:
-Pair 2 of the biggest fans that will fit. They should take up the entire radiator
-Use Spal fans. They are one of the only fans that actually move the air the are rated to flow at. They are rated in both pusher and puller configs, so finding two fans that are the right size and have the requisite flow should be easy. Fal fans are also legit, but fewer options are available. The Spal high performance fans move stupid amounts of air, so I use one of those as the main puller on my car. I'm using a large Spal slim fan as a pusher. For reference, I have the model numbers listed for the two fans I run on 1837 in my member showcase.
-Don't use a shroud. It won't help you unless the design is shaped and created to enhance flow (think any OEM shroud you've ever seen). An aluminum box is not a shroud, contrary to Mishimoto and most of the DIY shrouds I've seen done.
You'll also want to run everything directly off of battery power. On my personal cars, I run a hot wire from the fans straight to the battery. Then, I use the factory relay to control an additional high amp relay that works the ground side of the fans. I run both fans together, which works great. It typically takes 15 seconds or less for the fans to bring the car back to temp at idle on super hot days. Configured this way, they also both run whenever the AC is on, which is preferable, obviously. It's also nice for staging lanes at the track. I just kick on the AC and the fans work well enough to drag my temps down below my thermostat's opening temperature.