Thrust washers at the top of the connecting rod around the wrist pin will keep it centered on the crankshaft journal. Use brass or bronze washers and fit the clearance on both sides to around 0.25 MM or so. I think you should find a "mechanic" who isn't too timid to do things the easy way. A short TIG weld in a few places to hold a spacer onto the connecting rod cap won't damage anything, and it's a much simpler process than making a dozen precision thrust washers.
Jerry

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