If the flywheel BB is about 5/8" "to the left" or below the bell-housing pin, that would be about 5 degrees BTDC. The BB is in the flywheel at about a radius of 7", so that would imply that there would be about 8-3/16 degrees per inch at that location (360 degrees/(2 X 3.1416 X 7") = 8.185 degrees per inch). Is the BB at TDC? My 1955 shop manual indicates that it is.
Since the hole in the bellhousing is only about 5/8" on either side of the pin, you cannot set much more advance with a convetional timing light. Timing marks and a pointer could be added to the crankshaft dampener pulley, or use one of the new "adjustable advance" timing lights, as mentioned by BigSix302.
How much total centrifugal advance is in your HEI distributor from Tom? The 1955 shop manual says 12-14 distributor degrees for the 1955 engine. Thus (for the 1955 distributor) the total timing would be 29-33 crankshaft degrees with 5 degrees of initial advance.
