My '37 has a frame very similar to your '41, it had these brackets welded to it when purchased it in the '90s, it had sat since the early '60s before that. You can get an idea of where the top mount needs to be. I added a plate to the top which makes the shocks lean forward about 10 degrees to soften them up some. It helped the ride. If I could find non-gas shocks in the length I need, straight up right would be OK, but the gas shock work to good and needed a little angle to them. If the kit doesn't come with shocks, be sure to get a common one that's easy to find from multiple manufacturers, it will save some head aches down the road. I think mine are Ford Pinto rear shocks!
