distributor install problem

I am putting my '99 (5.7L) back together after a valve job and can't get the distributor to seat correctly. I believe that it is engaging the cam, but not seating on the oil pump.

In hindsight I should have put the engine at TDC when I pulled the distributor, but I didn't. Now when I put the engine at TDC to install it, obviously it won't line up. I found a website that suggests turning the distributor counter clockwise and seating it to find the orientation of the oil pump, but I was not successfull with that. The distributor has 12 teeth, which means that each increment is 15 degrees so it is entirely possible for the oil pump slot to be within one of those increments.

The GM manual says to use a screwdriver to turn the oil pump. My longest screwdriver is longer than the shaft on the distributor, but I was not able to engage the oil pump shaft even with the screwdriver completely down in the engine.

Is there a tool I can buy to align the oil pump slot? or is a screwdriver the best option? What else can I try?

Screwdriver. One that's at least 12" shank length. You might find it helpful to have a small light, like one of those LED keychain lights, to aim down into the distributor hole so you can see where the slot on the driveshaft is.

We've been doing it that way for years.