MOSFET selection for high current application
Sometimes the problem attempting to be solved needs a completely different solution that what seems obvious at first. Often the first blush choice is a brute force method that is just not really practical. I suspect that your attempt at this MOSFET reverse polarity protection may be one of those cases.

If you take a look at a familiar high current application such as the 12V battery in an automobile you will not see reverse polarity protection used. Instead the solution is to apply common sense in installing the battery using semi permanent bolt-on connections to the battery and starter.

Another example, although an AC circuit, is that plugs and receptacles for high current applications use special contact arrangements to prevent improper connections so that live, neutral and safety ground connections do not get mixed up.

Yet another example, this one a DC circuit, can be seen in how battery operated power tools connect to their battery packs. Special packaging has connection keying to keep from attaching the wrong way.

You may want to reconsider your application carefully so that you do not have to resort to multiple large MOSFETs attached to a big heatsink with active fan cooling.