Brad another difference is the wall thickness of the chrome moly tubing. It is thicker on the 78 model than any other magnum model or progression. That is why "some" prefer it's rigid strengh as a choice for a freinken bike. I suspect that one of the reasons that all 1981’s will eventually crack in the usual places if not gussetted first, is that the factory got over ambitious trying to save weight by again reducing frame tube wall thickness.
