Since you don't have access to the deck at the moment, it's difficult to verify the actual size. I have a 782 with a 44C that is basically the same size as your 1450 and my deck sticks out about the same. Yours would be a 44A. The "A" is a 1/2" belt, the "C" is a 5/8" belt. Partstree.com has your diagram of both tractor and deck. Try
http://www.onlycubcadets.net for a 1450 manual (don't have to join the site; scroll down to "Technical Library - Tractors," then go to page 4, and the 7th item down labeled "Manual - Operators Q/L Series"; can download a PDF of the 1450 Owner's Manual). Although, there are many very knowledgeable people on that site who know every nut and bolt of your 1450, so joining up would be a suggestion.
Your best bet is not to order any belts/parts until you get to the tractor and take some measurements. Auto parts stores like NAPA and O'Reilly usually sell Gates Power Rated belts. Take your old belts into the store and size them up. But you'll know pretty quick when you measure across the widest part of the deck/blade tips whether it's a 44" or 50".
BTW: If you have any side-to-side play in the spindles, that means they're shot. There are steel and aluminum spindles. I believe the steel ones are the oldest design. The aluminum spindles can be disassembled and have replaceable bearings; not so for the steel. I did a deck overhaul on my 44C some time back and posted pics. Located here:
http://www.farmallcub.com/phpBB2/viewtopic.php?f=2&t=90029&hilit=spindles