well im no profesional but i'd make some sort of housing.
i'd cut up sme scrap mdf or something like that, make a housing, slide the block into it, screw it down & slide the head unit into it. the housing might have to have a small clearance of a millimere or so on the inside, is better it be bigger so some spacers can be put into the sides to secure the block.
I dont know if anyone may be able to recommend something other than mdf in here but the thickness of the material used will depend on the clearance you have bewteen the housing & dashboard.
I saw raidb
imported something to fit a mazda 6 to replace the stock dashboard face so an aftermarket headunit could be installed. I dont know if any from another car might be able to fit yours or if there are ones available for yours.
http://forums.trinituner.com/forums/vie ... &&start=80
what headunit is it btw?