Trouble removing bolt from power steering pump...

I'm trying to replace my power steering pump, and one of its three bolts is near one of the engine mount bracket bolts on the powertrain mount. I cannot figure out how to get to the p/s bolt, and I don't know how to remove the engine mount bracket bolt.
It seems to be some strange size smaller than 3/4" but bigger than 11/16"

Has anyone come across this problem, or ever replaced the p/s pump on their '97?

I'd really appreciate any advice you could give.

Thanks

Just in case anyone else ever has this problem:

The bolt was 18mm -- at least that's what I took it off with.

I am having noise problem with this power steering pump, either pulley or pump bearing seem to be out of order.
My haynes manual said you need flex socket or U-joint socket to take out the one bolt near engine mount. I just called GM and they have exchange program. By the way, the real problem is removing pulley, I need special tool to remove and install. I do not want to buy another tools just for this. I am going to call dealer that they could remove and install the pulley for me with small charge.

Oh, one more thing.. You need to remove one big bolt on engin mount near the hole.

The bolts are removed through the pulley holes and the bottom bolt is removed after the mount plate is removed. To remove the mount plate (2 bolts 2 nuts) you first must support the engine with a block of wood, as large as the oil pan, on top of a floor jack.