The 3n71b automatic transmission in my 85 720 is getting tired after about 300,00 miles . I have found a low mileage (64,000) replacement transmission in an 86 d21 with a v6 in it. My question is "Is there a difference in the bellhousing behind the v6 and behind my NAPZ engine? " I know these are separate bellhousings which bolt to the transmission but I am curious?