To answer your question it is doable but very tight and time consuming. I have one in my day cab 6x6 and it is tight!!! Mine is also squeezing in a second esc in the drivers fuel tank and a second battery under the deck plate in the rear just to run my low boy and dump trailers.
Like I said it is able to be done but definitely don't plan on having any interior room left at all.
Here are a few shots of my truck with an mfu in it.
Hope this helps answer your questions.
Tyler