I have recently acquired to rolling chassis Kx 500s , one has a production date of 7 month of 1987 and the other is the 9 month of 1988 . Can I assume that one is a 1988 and the other is a 1989 ? The bike I am hoping to use is the newer of the 2 . The older one has some frame issues . I am looking to know which motors will fit these bikes . Thanks for any help I am brand new to this site and very excited to do a restoration on a KX 500 !!