Help! 73 sport seat rebuild!!!!!

I have done some front and rear seats before, with legendary stuff on GM cars, and I have used a lot of that cotton, but there was a small layer of foam below it. Usually you put the burlap with the felt on the sides of it first onto the frame with a ton of hog rings, then one piece of thin foam with more hog rings, and then 3-5 layers or cotton, then the muslin with hog rings, and then the cover goes over with another ton of hog rings. Legendary may be correct in that your seat was all cotton with no foam, but I have never done one like that. I would call them again and verify that your seat originally had no foam. They have a really good YouTube channel with how to install their covers, it is very detailed, but not every car is there. they do have quite a few Mopar seats so take a look:
https://www.youtube.com/user/legendaryauto