OK I'll try to start. Cross steer with a spring behind can be done, but it is tricky and even then not an ideal setup.
I think in your second question you are referring to a tie rod, not a drag link. The tie rod connects the spindles to each other, the drag link connects the steer side spindle to the steering box. So yes - the tie rod can be moved out front, but without modifying the steering arms it throws off the ackerman angle. Not the biggest deal in the world, but it also looks ugly IMO and isn't very safe. Keep it behind the axle if at all possible.
Yes, you can put spring pivots on split wishbones if they are properly gusseted and set the correct distance apart for the spring being used.
Finally, if the axle you have is a all-stock '38 you will NOT be able to use the brakes because they are mechanical. You DO need the '38 spindles however. With those you can use either the '38 axle or the Model A axle, depending on which you like best. As far as brakes go, if you want original Ford hydraulics you can use '39-'48 drums, hubs and backing plates or you can use any number of disc brake kits available for the '37-'48 Ford spindles. You can also use F-1 or early F-100 brakes with the proper bearings, but that starts to get a little more involved.
Hope this info helps you out...