The PB issue only applies to very late 84 and all 85 engines. In reality, thats only about 15,900 1985 engines affected vs a little over 95,200 1978-84 engines that can use the stock PB. So the chances of someone running across this issue is relatively small.

Nobody is sure as to why MB made the change so late in the game. It may have been just when they switched over to the high-stall torque converter along with the 2.88 differential. I do know that there are 13,000 or so non-turbo 300D's produced in 1984/5 and alot of them were sold with manual transmissions in Europe. However, I don't know if the smaller PB issue applies to them or if it's unique to turbo engines in the USA.