I use the
gates catalogue .
Click on the red "Vehicle Pars Search " button then on the next page click on "interchange" then type in the Toro part number you found in the IPL Rivets linked to
You should then get the Gates exact equivalent belt number pop up , it will have a "BR" ( Blade Runner ) part number if there is one .
Clicking on that "BR" number brings up the specfications of that belt ,
Gates have the only reliable belt specification page .
Most of the so called cross refference charts will cross your 86.75" belt to a 87" std belt