PM me pics of the inside of the truck, What tpe of subs are you wanting to do? What size, and How much power are you going to be putting to the sub(s)? Are you looking for a street beater or burp box? You looking to do a wall or no wall? Let me know and I'll help you out.
GalacticMonkey be carefull with bassboxpro. Use it as a basis to start. The program is designed for home audio applications. I oly use it for calculating port length.