Looks like the right mechanism. The bar is on top on the later ones, like in Shaffer's last pic.

If you have a welder, you could put a few tacks around the hole where the shaft goes and then redrill or grind with a dremel tool to the right diameter to fit the shaft. If the tabs break off, when you take it apart, the assembly could be tack welded back together.

Repops are available as well, if the repair attempt goes to hades in a handbasket. Link

As far as locking, there's an adjustment that can be made as the holes are slotted to allow rotation of the mechanism.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.