W201 OM602 IP swap
 

Replacing crush washers on my IP just made it run even more rough, so I'll be pulling one from the parts care to see if that will improve the situation.

Looking at this procedure:
I'm confused by step 3, with the timing basket

Remove Vacuum pump (held on by 6 - 10mm bolts). Install timing basket if not there.

What is the timing basket, what's it do, how do I tell, and what do i do if I don't have it?

Having a parts car hopefully doubles my chances of having a timing basket.

The timing basket holds the IP sprocket in place. Early model engines with early vac pumps had the basket installed as standard. Newer revision vac pumps require the timing basket be removed either because it interferes with the pump itself or the revised gasket.

So, if the new engine (my 87) does not have it and the parts car (84) does, does the old vacuum pump have to follow the IP, or will things work without it?

No, if you're just moving the IP over, the vacuum pump doesn't have to follow.

Pull the vacuum pumps from both engines and see if they have a basket. If the old one does and the new one does not, pull the IP and basket from the old, install the basket on the new, swap the IPs, remove the basket, and reinstall the original vacuum pump.

The basket will hold the sprocket in place so when you slide the IP into place the shaft will be lined up for you. Make sure you have the locking tool for the timing notch within the IP and make sure both engines are in the right place in time before you begin surgery. :)