I have a used 2.0 shortblock. it ran fine. I was setting the end play and I noticed that the rear main bearing can be rotated about 1/16th of an inch (by hand). it is not loose but I can move it.
Is it time to stick a fork in it? Is this bottom end done?

Tear it down, inspect the case. if it's undamaged, measure and grind or polish the crank, replace the bearings, the cam, and the lifters, and make it a runner. The Cap'n

I dont want to hear that.
tell me sweet lies. tell me it will run just fine

I took it apart.
loose end play beat the thrust flange. a new rear main bearing fits in the case tightly. teh old one moves fore and aft. ..but teh journal's surfaces are still cherry

does the case now need to be line bored? how tight does it need to be when test fitting? how much crush is required? should it be able to move at all?

Hell yes it needs to be align bored.... If it can be moved at all the case saddles have lost their crush. Those bearings and their crush is a crucial measurement that greatly effects oil pressure and oil temperatures and if it doesn't have the proper crush it'll lock up.

You may also have a collapsed main saddle, something that can only be measured with specific TIV tools made for the job- most machine shops have never heard of it.

Get that case checked out by a TIV specialist- if you need bearings I have align bores in all the sizes- they can be HELL to find.
BTW- If you find someone to alignbore the case and they don't already have the bearings- run away from them, don't let them touch it till they have the bearings that are going to use, measure them and determine the crush... Bearings these days can vary by .002 or more from box to box.

how much to send the cases to you? what is the best time and method to contact you about this