its best the subs have their own box space, and not sharing it with lose items in a compartment
whilst youve got your interior stripped out, dynomat everywhere to stiffen the panels, doors, tailgate, floor, etc
to add actually, and this is the bit i have no idea on, so im guessing someone on here will, im assuming your subs will be in 1 box, so you might need to work out the size of the box needed for maximum quality and getting the best from them, its usually in the tuning of the box
what ever subs you go for next, look at dual voice coils imo
with all this in mind, and hopefully someone can ellaberate on it, it should sound sweet