Yup...the 3rd starter bolt is a bitch. Just like others have stated, you need a combination of extensions, a swivel all reaching the length of the engine. It helps the car is up in the air, but can be done on jack stands. Youll be feeling the 3rd bolt blind as you adopt extensions towards the front of the engine. Might need to slip through the engine mount, might need to unbolt engine mount and raise engine a little, youll get it tho. Every modular owener, car, truck, van, rv, whatever has this experience.
When replacing the starter, only use 2 bolts in the accessible location. Leave 3rd bolt out. Function just