Its harder to find a tweeter that will play as low as where an 8" driver leaves off. Usually if your going to run such a large woofer then you will need a mid-range to handle the frequency between the woofer and tweeter.
So not only do you need room for a 8" woofer (mid-bass) but also the mid-range too.
you also have to have "crossovers" to separate the frequencies to the speakers. You will need highpass, lowpass and bandpass filters for a three-way setup.
There is a lot of space for a large speaker in the factory area but it will need modified and baffled. Don't expect actual "sub" bass to come from your doors that is just asking too much from a flimsy metal door.
I am planning on running two 7" rs180 woofer in a two-way setup with a nd28f silk dome tweeter. These work in a two way together because the tweeter can play down to 2000hz which is right where the woofer starts to break up.
Toreador Red 05' FX4
4.0 4x4 A/Tran Ext.Cab Daily Driver. Nomads, BFG M/T's
Alpine 9857, JBL MS-8 DSP, US Acoustics 2x80w & 2x100w, Vifa 1" XT25 Dual Ring Radiator Tweeters 3k+ 24db slope, Dayton Audio 7" RS180-4 Mid-woofers 100Hz-3k 24db slope, 500w rms Kenwood Class-D Mono - JBL 10" GTO1014 Sealed. 100Hz- 12db slope