I wouldn't remove the overload springs because with a light or no load they are not a factor in the ride, but with a load they're good help.
I'm not a fan of removing parts of leaf springs, they're handy for a working truck. Also to remove some can adversely affect how the rest act and can lead to broken springs. A pack of leaf springs is designed to work together, remove some and others get more work than intended. Not saying people don't remove some on occasion, but it might not be the best idea.
Sure you can add rear shocks. Here are a few pictures on how I'm adding rear shocks to my 2 ton, same idea works on most any other truck.
https://picasaweb.google.com/lh/photo/dn9V2vQ-EGSSQkWXu3xXHtMTjNZETYmyPJy0liipFm0?feat=directlinkhttps://picasaweb.google.com/lh/photo/2ADHCzRcBCC3z-zWeYncdtMTjNZETYmyPJy0liipFm0?feat=directlinkhttps://picasaweb.google.com/lh/photo/XTzkG6xsrAUBw5N5PhhG8tMTjNZETYmyPJy0liipFm0?feat=directlinkI think those brackets are from an IH or Ford medium duty truck, best way to find something like that is scrounge the junkyards with tape measure in hand.
The upper mount will be incorporated in a cross member for the goose neck hitch.
Grigg