Hi Joey,
I assume you mean the pilot bushing?
Unfortunately, you need the pilot bushing and you should install it since they provide support for the input shaft and keep it centered. You will have increased noise and vibration running without it and will eventually damage the gearbox.
Sorry, I understand the wish to not pull the transmission again (from experience).
Regards, Bill
EDIT: It can seem a frightening, but you should be fine. People on the forum will provide any information and/or support you need.
It is best to use a simple and inexpensive tool to press the bushing into place rather than drive it. I have an expensive one. But, you can find one for pushing bushings for $20.
If you do drive it into place, make sure you still have the recommended ID/clearances before installing the gearbox since driving the bushing can slightly close its ID.
I modified the propeller shaft tunnel slightly (added an end-cover/door) so it is much easier to install the transmission (something AH should have done). Most purists would never consider this, but the modification (i) can not be seen and (ii) makes it easy to lift the tail-shaft of the gearbox up and down when its pulled back during removal and installation (this greatly reduces required twisting and alignment gyrations).
There are lots of pictures posted online showing gearbox removal and installation. And, if you look closely, you can see many beat-up propeller shaft tunnels and tail-shafts. The tunnel modification also makes it easier to service the universal joint and hand brake; and seals well without the chance of any fumes entering the car.
Picture 2 shows the propeller shaft cover during fitting, and the red outline shows the actual size of the cutout in the stock tunnel. The silver "door" is a section from a Kilmartin propeller shaft tunnel that fits the original tunnel contours perfectly with good overlap for sealing. After painting, the modification looks "factory".
The third picture shows the modified propeller shaft insulated in preparation for installing a new interior. The only evidence that the tunnel has been modified is the insulation seams required so the cover can be removed when needed.