[MrPbody]

To add to what MR says, you're missing something fundemental.

ALL (American) V8s have two cylinders at TDC at the same time. GM and Chrysler, when the timing mark is at "0", are "up" on numbers 1 and 6. When one of them is on "compression" (both valves fully closed), the other is on "overlap" (both valve SLIGHTLY open). When your gears are at 12 and 12, #1 is "up" on compression. When they're at 12 and 6, #6 is "up" on compression. There is no possibility of bending valves under either of these conditions. The position of the rotor in the distributor is the only point of possible "error", making it 180 degrees "out of time", if you put it in "wrong".

Chilton, Haynes, etc. are written for the novice to be able to make his/her way through simple and moderate-level repairs. By telling you to put the dots at 12 and 6, they believe it's easier to get it "in time". The factory service manuals ALL say 12 and 12. If there's a descrepancy between manuals, the factory manual ALWAYS "wins". The "right" way to do it is to put both at 12, and use a straight-edge across the bolt holes for both cam and crank, and being able to "see" 1/2 of each dot. By placing them as far apart as possible (12 and 12), "deflection" is less of a possibility. The "ultra-right" way to do it is to degree the cam, making certain the intake "centerline" is in the correct position in relation to the crankshaft and piston. Degreeing the cam can be considered extraneous when using stock cams and timing sets.

Just for clarity.

Jim