BTW, the same drill-tap guide I'm building for the stovebolt engines will fit the early V-8 cranks, 265, 283, and early 327, that came without the center bolt.
Last time I dealt with this problem it was on an early 327. I did it free hand and don't believe I got it straight.
However it worked a couple years afterward before spinning a rod bearing while a friend was driving the car well over 100 mph for some miles on the freeway. Until today I've never wondered if my drill work had anything to do with that failure.
