I've never seen one. There's nothing to seal in or out of that area. If it would make you feel better you could always smear a little rtv between the two.
That's a great transmission btw, I've been beating on one for the past 10 years and it just won't die. I changed my differential to a 9" with 3.50 gears and I can still start out in 2nd. The T87D has a fairly low 1st gear.