Ughhhh, I feel your pain Rod.....
Make sure the builder, or someone you trust implicitly, examines the ring lands on your pistons, particularly #1 that blew. There could be microscopic cracks in them. I'd have a close look at them under a low power (maybe 50x) microscope, and/or use a fluorescent dye penetrant on them to magnify the existence of any cracks.
There's a number of educational type digital microscopes available for around $100 that'll connect to a PC (have a look on Amazon for digital microscope). One of these and that black light you've had in your attic since the 60's, ought to be just the ticket for doing this.