Hello, Trenches:
There have been minor and major variations in the dimensions and profiles of Armisport Spencer parts over almost 20 years. When the Ken Howell built 1860 prototype Spencer in 56-50 was sent to Italy by Taylors, the goal was for Italian Spencer parts to fit originals, but that did not happen for many parts. Taylors sent Ken to Italy after the first batch had problems. It's going to be a try and see thing.
I have seen a wide range of Armisport Spencer frame numbers from very early to within the past four years and some major parts, particularly levers and blocks were sufficiently different that they would not fit for correct block positioning and firing firing pin orientation. I took photo's of a stunningly beautiful rifle at the Winchester facility and its lever was out of correct battery and the top of the upper block was visibly lower than normal. One lever of a friend's Armisport carbine had to be bent to enable the firing pin to hit the primer. I have seen Armisport levers with the lower block screw HEAD on either the right or the left side of the lever.
If you purchase a repro lever, get one to match how the block head screw enters for your original and be sure you have the right to return it if won't easily fit.
All the best,
El Supremo/Kevin Tinny