Yes, those rabbit holes are many and deep! I know.
Not being an upholstery expert, I got my stuff from Beachwood. They have options all the way from bare frames to all the original internals in serviceable condition. Since I scored some nice seat pans to replace the plywood the jeep came with, I opted for getting foam to fit these that would sit on the frame.
I documented how I did mine on my thread on the old 3B Forum:
https://www.tapatalk.com/groups/cj3b_bulletin_board/green-gruntt-t4658-s40.htmlAlso used 3B Page article to get ready:
https://cj3b.info/Tech/KamunenSeats.htmlNot knowing what you're about to get into, I can only describe what I did. I noticed the drawstring seam pocket didn't have the durability to pull the covers tight (I did try and almost ripped the vinyl). My fix was to invert and compress (stand on the pan and smash the foam padding) so that the seam fit under the open tabs, without stress, before pulling the string snug (not tight!) so that I could coax each pointy tab down into the seam to hold it. Note about my seat pans: Since these were manufactured for a mil vendor (for M38 - at the time, no civilian vendor was offering these), I needed to sand the pointy tabs so they weren't so sharp and had to also pre-bend them open and then with a curve to bend back down into the material when closed. Unlike the 3B Page article, my tabs were NOT delicate. The back covers were much easier but start at the top in the middle and work down each side alternating otherwise the material may get lop-sided.
I don't think the later models were as difficult (they appear to be "slip-over" type).