on the seats, It is major surgery on the floors. You have to remove the "humps" where the floor raises near the rocker. Remove adapters from new seats and bolt down. The rear seats are about 3" too narrow. I had to "build up" a filler using expanding foam wrapped in black interior carpet, and yes, the rear seats do fold down, so you can pass through to the trunk.

I feel 2.5" TTI is sufficient. The motor is 370 cu in. Mikes tuning cost, I do not recall exactly. I pucrhased the diablo trinity from him, and that included some tunning. Just email him at mike@ostdyno.com

thanks