Will they have cheated me with a Ford Transit ?? aid

Good to have if you can help me, asking about Aki about a speed sensor and when I did not find the house, this van bought the 2 hand and according to the house the house the gearbox is changed and it has the one of the 110cv that takes the speed crosses from the ABS, and it is how it does not have ABS because it cannot be put, what can I do? How could this be solved? Is it possible to put a different gearbox than I used? Sorry for the tocho and I hope they help me. thank you so much