Going on memory only here but: Some of the Big Block engineers were consulted regarding the T/A block and early "X" & "R" race engines. Tom Hoover and the "Great Eight" group of engineers had influence at the top, (Lynn Townsend, Chrysler President). I was too young for Chrysler Engineering then, but old enough to watch prototypes tested on Woodward and elsewhere. I hope I'm not getting too far from Dan's original post, but I'm wondering where the X and R blocks were actually cast? Indy Foundry? Huber Foundry for T/A heads? If Mound Road Engine was too busy, who machined them? Galaxy? Sorry Dan, I'll stop if I'm out of line.