END THRUST PLATE.
You can get one of two different plates, but they must have the
oil groove in them. You say the lifter was worn on one side? It did not rotate as designed. Check the hole diameter against the other lifter holes. Make sure it is the same as the others. Pipe cleaner the
oil passages to that lifter.
Yes, you have to pul the crank gear when you pull the cam gear. Unless, of course, you have a Pete Jackson.
I did my top end last night. Got the lifters installed and the intake back on. What a pain!!! I hope the valley pan seals better with RTV than it did with rubber.
What stage are you at?