You should read my post about building one of these. They certainly do not fit easy and need extensive modification. I had fun doing mine and I like it, but it certainly took some time and hard work.
I still haven't had time to ride the damn thing (no snow!). My only concern is that the seat is significantly stiffer than the regular seat and I usually put on 150-250 miles per day when I do get a chance to go. I'm concerned that it might be too stiff for long trail rides. It would be perfect for ditch banging.
I have a 440 sno-pro seat modified to fit firecat chassis with tig welded aluminum sub-frame.
installation would take about 10 minutes. I built this last year and put about 1,000 miles on it and it is a firm seat, sits taller, great for ditch bangers. I just recently sold the seat, sorry.