42" Decks: why different hangers ?

[GlenPettit 1,717]

Here are three 42" decks, they all have a hanger system that is slightly different from each other and are not interchangeable (rear wheel  trunnion set-up), top 2 are RD, bottom is SD with Bagger assist, Would like to hang on 312's or 416.   Why are they like this and what should they go on?

Glen
 

[rmaynard 16,349]

Looks like at least two of them have ID tags maybe? That could help to determine what they fit.

[doc724 925]

I have had some of each.  All seemed to fit on traditional classic tractors.  Don't know why the SD deck has the extra middle bars, but maybe it is to provide support for the blower that will hang off the side for use with a bagger

[wrightorchid 261]

The bottom one looks like the same as on my 312-8.  The ID tag should have the model / serial number on it, so you can get the year and such.  I have not used the RD types, only SD.   my 312 has the lift on the left side, and lines up with the middle bar.