Youre not really annoying, youre new to cars so you dont know everything... it takes time. Were here to help so I just wanted to make sure people knew what the hell you were talking about. If we cant tell what youre saying, we cant give you the answers or advice you need.
Anyway, without getting into specifics, most older Nissan/Datsun transmissions are interchangeable. Thats why you see people with transmissions from 200zxs, 280zxs, etc. on their 510s/521s/620s. The bolt patter on the block and the trans are the same so they bolt together. That doesnt mean that they were made for each other. If you look at the L series blocks they are slightly angled something like 8*. When you bolt up a trans that was made for the L series, the shifter is adjusted -8* so that its straight up and down. The Z series blocks, they are slanted differently... so when you bolt up a Z series trans to an L series block, it results in a slanted shifter.
Like I said, as long as its not hitting the tunnel, its fine. It wont hurt anything. If it is hitting then you may have either bad transmission mounts, they are loose, or when they cut a hole in the tunnel to run the shifter through, they didnt cut enough of it.
That piece you linked a picture to will not fix your problem. Its just a piece that bolts onto the tunnel so that there is a tiny whole in your floor when youre driving it, but when you need to work on it, you can unbolt it for better access.