Yes there is an inspection plate on the lower front of the transmission housing. The plate is sheet metal, is vertical and is held in place with a few small fasteners.

You have another problem, however, if you are blocking the balancer and turning the crankshaft, you do not have any pins in place. There are two metal dowel pins that key the balancer in place on the crankshaft. These keys are what prevent the balancer from turning on the crankshaft, the bolt just holds it firm rearward so that the pins are held in place.

Pull the balancer and look at the relationship between it and the crankshaft and I think you'll see what I mean.

It could be that the notches in the crankshaft and balancer are damaged so that you can't really tell what's going on.

If you will search harmonic balancer in the diesel discussion forum, you will find much information about this.

Good luck,