I've been looking at a similar project.
The 368 was so despised that the pistons are now Unobtainium. Flatlander says their listing is for "historical purposes only", and they can't get the pistons (but the listing does direct traffic to their website!).
$895 for a set of 8 Venolias is more than we'd likely pay for a set of 6 "custom" pistons from Ross, JE, Egge, or one of the other fine suppliers. So we may be better off finding out what bore our blocks need to clean up, what deck it needs to square up, what piston height will get the right quench, and what piston pin geometry will work with our rod choice. And then order *exactly* what our motor wants, not something close that was "off the shelf" at one time.
While designing pistons and deciding bores, also pay attention to available ring sizes. I'm looking at the Total Seal Gapless; they have a few options for the 3.80" bore and a couple of oversizes.
One other option I'm considering is the 3.0 Buick piston, with a longer (custom?) rod. Not sure if I'll stroke it yet, need to finish looking into the rod clearance question.
And 12 Port, the math on 261 = 235 stroked like the Cadillac build doesn't work out. 3.5625" (235 bore) with a 4.125" stroke (a la Cadillac 261) becomes 247 cubes. Overbore it 30 and you get 251. Overbore it 60 you get 255.
