Get your mechanically-inclined grandson with flexible small fingers to crawl up on there and go to it!
Some like to lay a board over the engine and lay over it to work on it from the other side. Can give a better angle to reach in there.
Can also loosely bolt the bussbar to the GP and use the bussbar has a "handle" to guide the GP into the hole and tighten it in, then tighten the bussbar nut.
Have extra nuts on hand so when one drops into the never-never land (never to be found again) it doesn't end your day.
Main thing is to alter the position of the IP at the next IP timing session so it sits angled further out from the engine side, giving more room between it and the engine for better GP access.