Summit list a DSS 6020X-4057 forged piston for a 350 Olds. 4.057 bore. They have 1/16 x 1/16 x 3/16 rings. Compression distance 1.612, wrist pin 0.980. Flat top, 2 valve reliefs, -3.00cc.
Anyone know if these are good pistons? $549.95. Seems to be another option for the E block 400 guys.

 

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They look look quite similar to the no longer available probe pistons. Something more modern than the Speedo Pro offering.