The sun gear has, from the factory, a bushing installed on either end.
By installing two bushings on either side and drilling the lube holes that you have covered up, because of the additional bushings, you will make this trans more durable.
Go to the search feature, located at the top of this page and type in jakeshoe.
Then click onto the thread that is at the top of that page.
I think it is titled first time 350 rebuild, or something like that.
This thread will cover a lot of your questions, I think.