There are a couple of ways to do the install.Proper way is to gut the whole car...dash,heater box etc etc.Other way is to trim the pan lower down so you don't have to pull dash etc.We have done several C's both ways.When you remove the donor pan leave the seat braces attached.....less welding.If you go this route make sure the underdash area is well protected..underdash fires are nasty.65 to 68 pans will interchange but the 65 pan is quite a bit different shape wise to 68.This pan went into a 67 Monaco Fastop.