Generally speaking it’s pretty straight forward if you have two Fender spec necks and a body with a Fender spec pocket.
Usually the only issue you’ll run into is getting the neck fully seated and tightened in place properly.
A lot of builders (even Fender on a large percentage of their basses) drill the four body holes the same drill size as the neck holes. That means your neck screws will be threading into both the body and the neck at the same time. Not big a problem if you have a neck vise or sturdy clamp to hold the two pieces tightly together while you thread the screws in place. However, its not really the proper way to draw a neck tightly into the pocket. If done this way, your neck to body fit will never be any tighter than the clamp (or hand) used to hold them in place when screwing in the screws.
The proper way is to drill the body holes as a slip fit for the screws, so the only real thread grabbing is done on the neck (not the body). This will allow you to pull the neck very tightly into the pocket for a proper seat as you tighten the screws. Not sure how Carlo drills his bodies (slip vs thread fit), ideally they’ll be a slip fit for the screws in the body holes, if not, consider making it so by going up one drill size on the body holes only.