Starter wiring change due to swap

[gabbin]

I swapped out the 327 to an 87-95 355 roller, so the starter is different, on the older 327 starter, it had 3 posts, R, S, I,
The new starter only has 2 post R, S
The wire that was used on the (I) ignition is 12v constant, so I turned the key on and viola, I already have 12 at the coil, so I feel somehow the 3rd wire is redundant.

So my question to all of you is, should I just tie it in to the (R) (main battery) connection or leave it shunt and keep it, or pull it in the cab and find out where to delete it completely?

In my mind, I feel I should just shunt the end and always have a 12v source I can tie into if needed.