There are many differences between the 6 and 8....much more than one is 5 based and the other 8 based. Not only are there body sections that appear to be the same, but aren't(such as windshield, dash, fenders, ...),there are big differences in driving characteristics. If comparing stock for stock:
The 6 will have 4 wheel drum brakes, narrow track axles, may or may not have a tailgate, low back seats, a open c channel narrow frame, a wheel base of 101 for pre 72 and 104 after 72,etc, etc
As said before, like a 5 in drivetrain and most sheetmetal, but not any 5, the 5's of that time.
The 8 will have wide track axles, a wider frame, 104 inch wheelbase and share most the sheetmetal( not tub of course) as a later 7. I believe only the 81 8's have the narrow track axles. The 8 will also have a sway bar.
As a daily driver, the 8 wins hands down. Don't get me wrong, I wouldn't trade/sell my 6 at all!, but it drives like a farm tractor with no power anything and lots o'swaying in corners. My 7 is like a sports car on rails compared to the 6. I just drove back from GA for 4 hours doing 75 to 85 most of the time ,no prob. I wouldn't dream of trying that in a 6. It's just a different beast. Also as said before, many more parts for the 8 and 7. I too am in Mobile, Email me and I will gladly let you check out my 6 for a hands on look at body and tub differences.
1975 CJ-6 1983 CJ-8
1986 CJ-7 Laredo 1986 TJ-7 Trail Jeep
2003 Inca Gold TJ Rubicon