[Blas]

I believe the 300 series has most of the newer style interior improvements - consult the detailed list:
A link in an earlier post here leads to a great document the describes in detail the majority of the changes in the MKIII by chassis series. My intent was only to highlight what I consider to be the highlights of the factory related changes.
Seeing your prospective car close up, having the driver give you a ride, and then driving it yourself makes all the difference before a purchase. For instance; Dropped foot boxes may not make any difference to you if you are 5-'4" with size 8 shoes. I actually looked at 4 different cars before purchasing mine...
I think it's safe to say that car owners themselves develop a lot of great improvements to the standard chassis of any replicas out there, be they comfort or performance or safety related.
Enjoy the hunt.