It doesnt look like I'll have room back behind the rear 04 scab seat inless I mount my amps directly to the rear cab wall. How bad would this be ????

 

Does that mean screwing in/through the back wall? If so, no... I just have mine mounted under the driver's seat of my '03 reg cab... Same thing with my Sirius reciever. I just used some self adhesive velcro on the bottom. Just used the "loop" side... keeps them from sliding...

 

Amp rack? No - they are mostly for show. The only thing I'd worry about is the possiblility of excess rust where the screws punch through after a few years.

 

thats what I did. There are two small screws, and I sprayed some rubber undercoating all over that area. So they are well covered...