I may be thinking of something different but do you mean one or two piece rear main seal? Just going by the year I would say 14", but from experience, you never know anything from assuming
Your boat did not come with nor does it now have a 270 drive. Why do you think it has a 270 drive?
Probably came with the 290 which has the top cover like your drive did in these pictures from your previous post. http://forums.iboats.com/showthread.php?t=529057