The earlier Magnum .40, .46. and .53 XL carbs wont fit on the new .52.
The spigot is smaller on the old carbs, they use the cinch bolt....and
the spigot (nounting flange) is shorter. Also they are not drilled for the
two screw carb hold.

Your screw is a 3mm, you might look for a 3.5mm screw and tap. The thread
pitch has to be the same for both. You can buy single taps at True value hardware
stores. You could possibly go to 4mm. or to 6-32 American

Trying to fill the old hole with JB weld and re-tapping the threads to stock
may or may not work....

When you install those carb screws, you must hold the carb down real tight
against the o-ring.

Unless you are skilled at re-working threads, you might be better off just getting
another carb body. At least that way it will be back to stock....and back to
brand new condition....and a lesson learned.

FBD.