Ok, here's what I THINK.
The 41's all had the same crossmember. This crossmember has a deep drop and will accomodate the 6 cyl engine. It will also take the V8 and (I guess) the 4 cyl. They did not use different crossmembers in 41 for the different engines, thay all used the same one, the one with a deep drop.
I have a 41 and it has the deep drop crossmember. The engine mounts line up with the flathead v8 mounts.
The 41 rides a little higher than the 40 due to the deep drop crossmember. The bump stops have a 1" spacer built in. If you fit a 40 style crossmember (to help lower the front) then you should also swap out the bump stops and fit the 40 style that do not have spacers.
Again, this is what I THINK. If I have it right or wrong please let me know.
Mart.