What year did the stepside fuel Door start?

[2bits]

I just finished putting the bed on my truck, so it is finally complete! It is a 71 truck but I put a 73-87 bed on it. Some people don't like it, but I think it looks great. To me the 73-87 Stepside beds are the best of all the years and I just sold my 73 Stepside so I gues sI was missing it, not to mention my existing bed was trashed and I got this new bed for $250, so it kinda came to me. Enough excuses, here are some pics.

I was wondering what year range bed this might be though since it has the fuel door?

This first one was taken at MIDNIGHT in black night


The money shot:


Please excuse the pole


A couple more...