What is this part ?

Where is this hole? Can you take a picture and post it? The speedo pinion goes into the tailshaft extension housing. The B&M shift lever is clocked different than a stock lever so a stock lever won't work. If you didn't get one with the shifter you'll need to buy the B&M lever kit. Unfortunately when you buy that kit you'll also get to pay for a lever for a GM and a lever for a Ford just to get the one you need for a Mopar. That's why I never buy a shifter unless it comes with all the hardware.