Judging from your pictures you HAVE had the motor out for a body off resto. Did you do the work? Looks real nice. If you have a history and confidence in the motor, i.e.its been gone thru and you have a reliable tachometer or you let the auto tranny do its thing when you "smoke um every now and again", you shld be able to minimize any threats to your original motor. These were relatively hi po motors and built to take some abuse. If you routinely thrash your car, you may want to consider an engine swap - be advised the rest of the drivetrain is at risk too. Saw you installed chambered exhaust on your '70 and have a posting of the April '69 Chev. bulletin regarding changes to the NC8. Is that an original bulletin?
Enjoy and Good Luck!
