A little up and down movement in the rear output is normal, in and out play is not. the output bearing and seal can be replaced very easily with the case still in the truck. If you do this, don't forget to check the output flange for a groove where the seal rides, if it is grooved you need to replace it or the new seal will probably leak.
Now your confusing me
As far as interchangeability, I've always been of the understanding that all that really matters IS forward or top shift, when talking 4cyl non turbo cases. I don't think the shift fork and retainer clip difference have any effect on them being interchangeable, but Im not 100%. good luck
