Just to be sure, after I got up this morning I inspected the parts I have for you. Using a drafting triangle, the angle between the pivot post and body of the slide catch I have is exactly 90 degrees so we should be good to go there. Then I test-fitted everything into my own 4506 and it all worked like a charm. Even though these are used parts and apparently your 4506 may be high mileage I'm hoping that it all works out regardless.

I'll head down to the Post Office and get them out for you on Monday.