A guy on another board is using some custom Ross pistons in his 263. He goes by the name "Scotch". Checkout these threads for some of his posts:

http://www.jalopyjournal.com/forum/showthread.php?t=25465
http://www.jalopyjournal.com/forum/showthread.php?t=8368

If you contact Scotch he can send you the part number for the Ross pistons.


Also, checkout these threads for some more info on hot rodding a Buick straight 8:

http://www.teambuick.com/forums/showthread.php?t=9365
http://www.teambuick.com/forums/showthread.php?t=10371
http://www.teambuick.com/forums/forumdisplay.php?f=91