Sorry for the delay, work has been kicking my assets.
Also, want to correct an error from my earlier post. Mark IV and Gen V timing covers are indeed interchangeable. I have verified this fact between blocks that I have here. The Gen VI is different. I was not able to verify the thread sizes of the Gen VI block. The numbers in the print for the Gen VI are as measured while Beerjet and I were designing a billet timing cover for his engine. The numbers for the Mark IV and Gen V are compliments of Wizbang. The holes are symmetrical from side to side and are a true mirror image about the centerline of the crankshaft. Sorry about any confusion or inconvenience from my previous post.
Joe
