I was building one of the Plinker-style rear trunnion riveting jigs for a fellow, and decided to put together a few extras while I was at it. I have one left. Price is $70 + $8.10 for Priority Mail shipping. Total $78.10 via PayPal or money order..
Jigs are MIG welded with one inch nuts on 3x4x5/16" rectangular tubing. The clamping bolts have been faced on a lathe to help prevent marring of your receiver sides, and the hole for the riveting punch has been bored and reamed for accuracy.
These should also work well for setting the U-drive drive screws, using a press.
PM me if you're interested.
Updated with current price, shipping, and stock info.