You will get the best fit and service out of the proper IH belts.
The D&D belt you mention I think is a 1/2 inch belt and will be too short as it will ride higher in the pulley grooves, possibly even being rolled out or will roll over in the pulley grooves.
The pulleys are intended for 3/8 inch belts.
Lots of stuff in the tech library here and you can look up parts at partstree.com, or cubcadet.com, or ccspecialties.org.
Use your model number, 1450, under "garden tractors."
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