I have a 5,
but a few 6 to 7 SS differences that come to mind are ;

the firewall forward , engine mount puts engine out approx 4" further from firewall = extra room for maintenance

there is a boot cowl that can be sealed nicely to the firewall

larger elevator , about 4''

I believe the 7 SS control rod for the elevator has a pivot in it that is a little different than the 6

the 7 SS is built light , and registered at 1320 gross instead of the 6 at 1550 gross