don I go by the march 31st 67 nhra chevy specs blueprints for any yenkos after april 1st, the auto 427 nhra has hydraulic cam listed, it gives the intake number, carb number, piston dome hght, etc. all you would need to race it in stock class, interesting enough they list the alum head option only on a tripower stock, and no mention of the L88 till july of 68 specs, I assume harrell and yenko would set you up according to what class you intended on running so you didn't get bounced for having the wrong carb , ahra specs may have been more important for them in stock class in 67, just not sure??
I got from the harrell crew who were their then and know their stuff inside and out that it was an early block and extremely thick. I know that sometimes not all the old stuff made it out the storage rooms at gm and 2 and 3 yrs later they would go to the back and pull out some dusty stuff, could have pulled out 961 4 bolts L78s, and they were real thick, once they showed up in cars they could have safely bored them all the way over as the same casting was also used on a later 2 bolt 427, Ive read you can bore them to 454 bore if you can find pistons 4.375 big..
