When they mention Old Model, most is for the hammer guns. On the hammerless models, the top lever is longer for a Regular frame than a FW frame. The mainsprings have to be fit to most all.
The newest listing on eBay and Gun Broker is the top lever screw, it is zinc plated, in order for it to look right you have to torch the zinc off and recolor with Oxpho Blue or something similar.