Tell us about the car. What frame,and rear cross member are you useing,what rear radius rods/wishbone? Spring on top of axle,or behind?
Sorry Im young and new to the scene i have been building a frankenstein speedster. it is a model t frame. It has a 8ba in it and I have 1940 rear ended and wide five drums and wheels.
Take the remains of the stock bushing out of the spring and use a new shackle pin/bushing. The real parts houses sell many different sizes. You can either find the proper size for a 40 Ford and add some collars to take up the slack of the narrower spring, or maybe get lucky and find pins that will fit the spring and then can narrow the rear's hangers a touch.
The wheel base will look odd with the '40 axle housings moving things forward. Mice period way it the Isky Roadster setup with the housings swapped left to right, right to left this makes for a longer and much more pleasing look. Bob
If you mount the spring behind the axle you may have a problem of the axle bottoming out on the frame. Do some rough setting up before you get too far into things.
I will rough fit it may have to notch and reenforce frame. on the t spring what bushing do i need the stock bushing ?