Brian, a broken rudder stop flange on the bellcrank is not unusual. Not the best design. If you have a B model and the rest of the bellcrank is fine, a relatively easy fix (compared to replacing the bellcrank), is to add L-19 stop pads/bumpers over the bellcrank flanges (including the broken one). (You may be able to do the same on the straight 170 and A models as well, but because I don't have either of them, I don't want to say.) See this thread, especially the pics on the second page showing the L-19 stop pads/bumpers added to George Horn's plane.
http://www.cessna170.org/forums/viewtop ... +bellcrank
You can get the stop pads/bumpers from Air Repair, Inc.
http://www.airrepairinc.com/ 662-846-0228. They're good folks. Tell them you are a TIC170A member.
I did this fix to my plane at my last annual. Do both sides at the same time. Also, if the holes of your tailwheel spring tabs are elongated, you might as well change them at the same as the L-19 pads use the same rivet holes. At least for the B model, the L-19 spring tabs are the same as B model tabs, so you can order them from Air Repair at the same time. Here are the notes I made for myself from the same repair I did last year:
"6/2016 Rudder Bellcrank Stop Repair (Adding L-19 Bumpers and New Tailwheel Spring Tabs)
Bumper: L-19 p/n 0660341 Tailwheel Steering Tabs: L-19 p/n 0660071, C-170B p/n 0433132
Remove rudder before making the repair. The time saved by removing the rudder will far exceed the time it takes to remove and reinstall the rudder. The rivet holes are no. 30 drill size for no. 4 rivets. The holes of the bumper and new tabs match the holes of the for the original spring tabs on the bellcrank. However, it may take some adjustment of the forward edge of the bellcrank (at the area of the rudder stop) to get the bumper to align with the holes in the bellcrank. After taking the rudder cable off the bellcrank, slip the bumper on to the bellcrank with the offset rear hole oriented towards the outside and cleco the rear hole. Then try pivoting the bumper inward (toward the fuselage) to see if you can get the forward hole to line up. It’s likely that you won’t and will need to do the following: bend the vertical flanges on the bellcrank more vertical so they fit in the bumper (behind its front face), and/or file or shave off a slight notch on the forward edge of the bellcrank at the inward edge of the bumper so the bumper can pivot inward enough so its forward hole lines up with the forward hole on the bellcrank. (A Dremel works well make the notch -- remember to dress the notch with a round file to eliminate stress risers.) When both holes line up, it’s likely that the bumper will not fully line up with the rudder stop bolt on the fuselage, but contact it near its outer edge. That’s just the way it is. The holes on the bumper/tab/bellcrank are too close together to use clecos to hold the bumper and tab during riveting. You cannot even use a cleco in one of the holes while riveting the other because it interferes with both the rivet set and bucking bar. The bumper is made of steel and is “springy,” so you must use something to clamp it during riveting. Before riveting, buy a 1’ long flush head machine screw thin enough to fit in the rivet hole, along with a nut, and use it to clamp the parts together to rivet the other hole. (You need a flush head screw so the head does not interfere with forming the shop head on the rivet in the other hole.)"
These notes were specific to my plane, but I'm sure that there's enough in them to be useful to you. Once installed, I think the L-19 bumpers are far more durable than the stock bellcrank flanges.
I hope this helps.