Only Cub Cadets - 149 mower deck belt

Hello, so I am trying to replace the belt on my 149. It is a 38" deck, the ID tag is gone. The mule drive I have is the one with the straight pulleys---not the angled. The belt that was on there was between 78-80" but it was too short. I took a picture where the pulley was cutting into the axle. I ordered belt 490489R2 but--too short. I ran string around all pulleys and measured 80". Basically has anyone else ran into this issue and what size belt should I be looking for? When I ran string, I understand it was a little shorter because of sitting in bottom of pulley. Does this deck take a 3/8" belt? Thanks for any help.
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