87 GMC stereo dilema, Help! Need some more ideas!

[cmax87v3500]

So I have a 1987 GMC V3500 Sierra Classic standard cab, as of now I have a custom sub box with 2 kenwood shallow mounts in it, and it works good with the factory seat, and is only one notch forward of all the way back(yes i know it makes marks in the back vinyl of the seat, but it does not affect the sound, or subs, and does not bother me) I included some pics of how i have it set up now. but i have a bench seat out of a late 90's GMC that has the fold down center console, like the one in the third picture that i would like to install. (That's another GMC k3500 truck my father built). I am afraid after taking measurements and just doing some guesswork it will cram me too far into the steering wheel to be comfortable (I'm 6 feet tall, but like my leg room). i'd really hate to loose the stereo with the seat upgrade, but really want to install the new seat. One of our friends just bought another k30 my dad built, and we measured behind the new style seat in it, and with it reclined comfortably, and slid all the way back there is 2 inches at the top between the back of the seat, and the back panel of the cab beneath that rolled out area, and 7 inches at the bottom from the bottom of the seat to the back of the cab. Ive done the work and figured out i could fit a jl 13tw5-3 in a box that size, but i cannot afford those and they would not work with my amp due to the ohms being too low for it to be stable(kicker ZX700.5). Any ideas on how i could make the seat work, but keep good bass and not loose sound quality. or even better, use the subs i have now Thanks, this is my first post and appreciate any help available!