I have an 84, and the timing marks are as you stated.  I got mine to run best by not using the manual and setting the timing about 5 degrees advanced (to the left of the split in the block; about where the "bump" on the housing starts.)  Runs great here.  Also seems to time better without disconnecting the idle stabilizer.  Sometimes the ear is better than the machine.  Anyway, that's my two cents worth.  Mine ran terrible when set by the Bentley procedure.
George