Manxmodder,
You are exactly right, the trunnion was worn (see below). I'll check the bull gear shaft and bearings next.
I spent a while unscrewing, staring, and cursing at the ram assembly before stumbling across a helpful forum online stating that the ram must be removed with the lever and link still attached. I was trying to remove the lever from the ram first. To remove the full assembly, the shaper must be un-bolted from the table and lifted up to gain access to the link (this is not an easy task by oneself, the machine is heavy and unwieldy). Three set screws are removed, then the pin securing the link to the frame can be driven out. Next, the ram slides are un-bolted so the ram can be lifted straight up off the machine. A slight sideways movement once it's partway up, and the ram lever separates from the bull gear and comes right on out!
After placing the assembly on a table, it was immediately apparent that the trunnion bushing was severely worn, especially on the side facing the front of the machine. Also, the heavy amounts of gunk in the assembly had clogged up the oil feed hole to the trunnion pin itself. At the least, the block will need to be re-made. This should be easy, the part is solid brass. However, there was very little, if any, damage to the ram lever itself. The machining marks were still visible on both sides of the slot, indicating that wear is minimal. I have not measured to fully verify however.
Other notes:
* No discernable wear is detectable on the ram slides.
* The inside of the machine is full of gunk and metal shavings.