A-Ha! That thread mentions and old straight Sugino crank arm on the left. That won't generally work on 1990s MTBs.

Are you still trying to set it up with a straight Sugino crank arm on the left? They generally only fit frames with 126 spacing, maybe some 130mm spacing with a long rear triangle that allows tight chainstays for a while before spreading out to the dropouts.

You need a left crank arm with an offset to work on your 1993 bike with fairly short stays and 135mm dropout spacing.