It can wiered question but I try.

I was looking to possibility to rent in US offroad capable car (X preffered of course) with camping equipment. No luck so far.

Do You know any place which would have 4x4 trucks for rent. And I am not talking places like Moab with Jeeps for daily rental, I am looking to rent couple cars for week or two.

It is very easy to find such rentals in Africa or Australia ... but here ... are all the people driving hwy's and renting from Hertz's etc? and they will not let You go offroad anyway.