Should piston gudgeon pin retainers be replaced at rebuild?

Those clips in the pics, you should replace with spiral locks. If you have spiral locks to begin with and you haven't removed them...and this is a refresh deal. Leave them in and alone.

You can't replace one style with another as the grooves are likely a different width. Circlips and spiral locks have the pins machined flat... wire locks have a pin that has a bevel on each end to help seat the lock. If the lock groove is the same size he's OK... but I doubt replacing those OE locks with spiros will do anything except put little holes in his fingers when installing those little b*stards.