I realize that there are multiple ways to go on the interior. With that bright lime paint planned for the exterior, a wild interior wouldn't seem out of place. But, the exterior mods have been subtle and still resemble a factory design. I think it'd be possible to add in modern amenities to the inside (including seating) and still maintain a 60's image. I guess the question would be 'which features did a '67 'Cuda have that gave it that vintage appeal'.
I don't think there's anything that should be 'off the table'. I could still see digital gauges, the modern seats, etc... - But hopefully some of the interior's soul will remain.
You've managed to add on the Roadrunner hood bulge that seems to blend well with the car, still says 'MOPAR', and doesn't look aftermarket or TOO modern. The front end mods have kept the styling of the original "Cuda sheet metal while adding in a modernized look at the same time. I think it'd be great to carry on that sort of theme inside.