Full foam folding seat question

[CG]

I picked up this full foam folding seat from member burnem today. I recently learned there were more differences in our seats than I thought there was. I'm curious if all the full foam bottoms are the same on every year, or did they change up year to year. I have some pretty decent full foams but off of 71/72.

I prefer not to pay the crazy prices of a new foam, so If I can use what I have or piece something together I would be pretty dog gone happy =)