Hi so I am updating my 1984 nishiki cresta gt from a 5 cog freewheel to a 7 speed shimano megarange. The thing is it doesnt fit. So the extra length of the new freewheelcatches on the dropout or rear fork. So that means I need a new axle and some spacers to make it work. I am not sure which size is proper any advice would be appreciated thanks.