At the very end of your excellent, CAM SECTION tutorial, you say "now the rest of the rear can be welded on." WHERE does one get this elusive "rest of the rear" receiver section?
Is this the BRP repair section that used to be available once-upon-a-time? Maybe still is, I do not know. I'm just getting into the 42/53 thing.
At this time I don't know where to get one. hopefully in the not to distant future Wise Lite will supply them or you can use some orogonal parts if you can find them.