there are lots of posts about this and i am glad i went with the heat gun method over the dry ice method, because i can not imagine the job being any easier than it was using the heat gun.
this thread is for the next guy that wonders how best to remove tar from his or her floor boards in about 1 hour.
tip, get heat gun about 1 inch from floor, warm area, tar should start getting soft in a few seconds, them start getting knife under tar, and working tar off of the warmed floor panels.
i still need to remove the seam sealer but the heat gun and a wood chisel seems to work ok on this material.
debate now closed.