How to tell if a spring plate is the desired adjustable ones?
 

Are there numbers identifying the ones that have more adjustablilty?

You can tell just by looking. An adjustable spring plate is a two piece plate. Looks like this:

http://www.pelicanparts.com/catalog/...ring_plate.JPG

A non adjustable will be one solid metal plate all the way back.

Chris is showing an aftermarket Sway-a-way adjustable spring plate. More specifically, it's a G50 Sway-a-way.

The factory adjustable plates look like this:

http://forums.pelicanparts.com/uploa...onebearing.jpg

Note the two large bolts near the pivot. Those are the adjusters.

Non adjustables lack those bolts.

Oh, oops... Chuck, Did the factory ever make a plate that wasn't adjustable that way?

I'm partial to the factory adjustables. They provide adequate range, probably 1.5 inches total.

The sway-a-ways are heavy and the design is clunky.

To each his own.

Chris, yes the factory plates before '76 (I think) lacked those adjusters.