The enginuis should work for you. You can add a 30 or 60 foot antenna extender that will pretty much cover 3-4 mile range.

I've done a few of these. One note though the SN920 not so much but the 436/490 we've had a terrible track record with.

When they work they're great, but I've had a string where I replaced 4 in less than 8 months.

Corwyn