According to a PDF of some old literature I found on the web, the 420mm f/9, 455mm f/9, and 480mm f/9 all use the same 90mm x 1mm flange. I'm not sure about the printing date, it might be 1982, and I've no personal familiarity with these lenses so can't say if they varied over the years. Here's the complete list:

180mm f/9 53 x 0.75
240mm f/9 53 x 0.75
305mm f/9 72 x 1
360mm f/9 72 x 1
420mm f/9 90 x 1
455mm f/9 90 x 1
480mm f/9 90 x 1
610mm f/9 110 x 1
760mm f/11 110 x 1
890mm f/11 162 x 1.5
1210mm f/12.5 162 x 1.5
1780mm f/14 213 x 1.5

Don't drop that 1780mm on your toe, it's listed at 6.43 kg, a bit over 13 pounds.