Some call them "Lincoln Locker" based on the Lincoln brand of welding units. The Roadkill guys have done it several times. One was a 73-76 Dart with a 7 1/4" axle. They welded the side gears to the differential case for some drag racing action. They had a fairly stock 318 or 360 in the car, I don't recall. I do remember that they sprayed a LOT of nitrous through it and got the car into the 11s. I have several 8 3/4" dropouts, maybe 3 of them are 3.23 open diff. I am thinking of giving it a try. The car is a beater. I haven't even registered it since 2017. I drive it around the backyard here sliding in the dirt like a redneck. It sure is a lot of fun. There is a 4.10 Sure Grip in it now. I know that these welded differentials are spooky on wet pavement and tight turns. I'd like to hear from guys that have done this to their cars.