When I saw the recommendation for Egge pistons, a "red flag" went up. While Egge makes a decent product, and one can certainly get them to make stuff nobody has made in 40 years, using them for Olds or any other "modern" application piston could be far more expensive than it appears. We do a lot of "mix and match" with bores, strokes and rod lengths. For less money, one can have "custom" forgings using better techniques. Speed Pro and Icon also offer a good forging for reasonable money for the Olds piston.
Bear with me for a moment. Consider this: Using your existing 425 crank, you can offset-grind to the desired 4.3" stroke (we're not gonna quibble over .003" here) and end up with a VERY desirable 2.2" rod journal (BBC). The Caddy cranks are good nodular units, so this will not weaken it significantly, and if the radii are ground properly, will actually strengthen it. Using the Eagle CRS7100C3D rod (narrowed back to BBC size) and a "custom" piston (of what ever bore size you desire) with a pin height of 1.52" will put you right there, with MUCH better parts for about the same money. The BBC rod bearing is .060" or so "wider" than the Cad, but narroweed bearings are readily available.
After looking at the various combinations available with factory parts, I'm thinking a better approach might be a 500 block and 368 or 425 crank (4.255 x 4.03). That makes 467 CID with a "big" bore and shorter stroke.
There are many performance parts available for the Cad these days, as it's a popular engine among the "claimer" roundy-round crowd.