I have both Scorp and Beta transmissions lying around my shop, they are nearly identical externally. The only real difference I see is that the Scorp unit is like the X1/9 in the output shaft area, where the CV shaft connections are close to the ring gear and equidistant from it. On the Beta, the short side has the same arrangement as the Scorp, but the long side has a shaft coming out of it, that runs near the oil pan rail across the length of the engine. Then there is a support bearing at the "front" (accessory drive) end of the engine, and on the other side of that is the mount for the CV joint. That must be why people use 2 short X1/9 axles. If you do use a Scorpion transmission, you would have to use the Scorpion drive shafts.
There is also a difference at the CV joint between the X1/9 and the Lancias, one has nuts on the other side of the 6 Allen-headed cap screws, the other has no nuts and the cap screws thread directly into the mounting flange. No big deal to overcome.
I can take some pix of the different units and post them if you want.