well you see that truck in my avitar? thats my truck. was told i have plenty of room for 2 or 3 15" . i dont think ill go with 3 but you never know. ........ lol.
i pulled the back seat, so i have from the back of my seat all the way back. thats about 8-1/2 feet, by 35" wide ( could go a little wider if i pulled my wheel well panels ) and i have i think 39" from floor to roof.
right now with 1 15" in ported box, buy looking at the size i could put 4 15" in my truck.
so i think i have enough room for 2 subs,,amp rack,, 4 batteries ( maby more ) , well see 1 thing at a time.