Many have tried, or at least dreamed about this. I can safely say the the hardest part of this coversion is the shift linkage. It seems that everyone has a slightly different take on how to get it done.
Mounting the engine/trans is 'easy'. The driver's side rail has to be notched to clear the trans, new mounts have to be made, and a remote oil filter is needed if you don't want to cut a lot. I have seen the waterpump from a Ritmo 130TC used (it includes a mount), but they are too common in the states.
The shifter can be a modified Scorpion (through the firewall), 'under' the bellhousing rod, or cable..... I have only personally seen a modified Scorp.... There were pretty good photos of a Faran conversion somewhere here on the forum, but all of the others seem to be a mystery. If someone were to post GOOD photos/diagrams of the shifter mech, it would really help people like you.
Most people consider this swap too difficult for the rewards. The Scorpion is a totally different animal and the handling of the X would be completely different.
Also keep in mind that the Scorpion is different than the Beta in several subtle ways. The later Betas have equal length halfshafts (you would use 2 short 1500 X axles) while the Scorp does not (would require 1 custom axle in an X). The shift mech is also different including the shift rod coming out the TOP of the trans and the Beta used a cable clutch release.
If you try to use the Beta FI system, you will have to modify the firewall (as well if you use dual carbs).
Do you have a supply of Scorpion parts already? If you are still interested in this conversion, I have a lot of parts.