Here is a list of things I've done to my '54:

Vortek PG2 kit with a 17 ft. lb. spring (settles down to 16.24 ft. lb.s)

replace shroud with: 17MM X 15MM X 400MM 100% Carbon fiber Wing tube from eBay.  Make a flapper sander from a dowel, cut a slot in the end of the dowel, insert a strip of coarse sand paper, chuck dowel in a drill, run up and down inside tube until it's a snug fit on barrel.

Removed action lever metal piece.  The thing the cocking lever levers against to push the action forward.  Take that out and just push the action forward with your thumb.

Added a rubber o-ring to the forward slide rail as a recoil bumper stop.  Added a thin washer to the rear slide rail to prevent the detent ball from completely fitting into it's hole; by having it only about 1/2 way into it's hole there is even less felt recoil as the ball is forced out of it's detent hole during recoil.

Replaced stock screws with a threaded rod (long screw with head cut off).  Cut a screwdriver slot in end of rod and use spacer, and nut.  Tighten rear nut with a socket with a screwdriver fit through the socket hole to prevent the threaded shaft from tightening down onto the recoil tension adjuster.  This prevents installing/removing stock screw from changing tension adjust screw setting.  Allows the stock to be really cranked down without concern over running into the tension set screw.  Forward nut doesn't have the concern, just tighten the nut.

Scope mount made from two UTG mounts.  Wrap scope in clear tape and glass bed with 5 min. epoxy with shims to shoot on center @ 25/30 yards with knob centered.  You will need a lot of tilt, so expect to replace rear ring screws with longer.