99 motor into 05 aluminum frame, and vice versa, and other annoying questions

I'm going to make the wr300 a reality here within the next month or so. I currently have 2 yz250s, a 99 and an 05. I'm going to build the 99 motor into the wr300, so that I do not need to have my 05 down while the work is being done. Then I plan on swapping the motors(putting the stock 05 motor into the 99, and the new built wr300 99 motor into the 05). The issue seems to be the swingarm pivot bushing at the back of the motor. I am unclear whether this is a bushing in the motor, or whether it is the back end of the case itself. Can I just take the 05 bushings and tap them into the 99 and vice versa or do I need to have the 99 bored out, and then get the 05 shimmed to fit into the 99 frame?

That is annoying question number one, but I'm just getting started. I'm rebuilding the 99 motor completely. New bottom end, new everything. It is my understanding that the 99 motor and the early 2000s motors have a different thread on the end of the crank, and therefore can use a different after market stator, which is easier to find and or better? Am I crazy here or is that real? Do I need to order a 99 oem crank to keep this option open?

Please help me out here. Thanks guys.

First question, yes you can just tap the bushings out and swap them.

However your kick start will remain the 99 model. It fits and works. Cosmetic only.

You could swap the side cases and kick shaft assembly off the 05 and that will fix it.

Question 2- the stators are the same so no problem. Yes the crank is a little different so you should stay with a 99-00 crank.

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