If you have a 7/8" then almost any bmx from the 80's will work. However, many schwinn's from the 60's are 13/16". In that case, that was a rare bmx size used by pk ripper and very few others. I've seen Tuff-Neck lay back posts in that size as well. Not cheap. Getting one made by a welder is probably cheaper if you have 13/16".