I'm a total novice here. I have a 2003 8' Supercab. I've located a topper I like that was on a 2013 8' Supercab. Are these compatible, or are there subtle changes through the years that make them not so?

 

The changes are more than subtle. It will not fit. You have to stay in the same generation.

 

And to complicate things even more and I'm not sure this applies to the 8' bed. But, the regular cab with the 6.5' bed has a different camper top than the supercab with the 6.5' bed. The rear of the cab is shaped differently and if you use the cap for the regular cab on the supercab, the cap will rub the 3rd brake light. I used one for a while before someone told me the difference and I found one designed for a supercab. Supercabs with the 8' bed are rare so good luck finding one that fits.

 

I never liked camper shells. I'd rather install a tonneau cover. Just my personal preference.