Re: 4 speed on a 4.1
an electronic box will be hard but I think you may be able to fit a 4 speed hydrualic Turbo box from a holden if it fits in the trans tunnel. The custom adapters are around $700.
Or you could do what I did. Leave the 2.92 or whatever you have and fit a 351 in place of the 4.1 and have power and nice cruising to boot.
Twin Cam EA falcon
SWB Ford Maverick