I read about them, but still cannot think of perfect belt… Maybe someone with more knowledge can suggest which would be the perfect belt for this configuration.
Anyone with extra belt and lives near chicago city, have a belt that suits this configuration , i would be willing to buy.
Do you know the width you want to run? Do you plan on using single or dual drive? Did you buy the motor mount already? What wheels do you have?
Also this calculator might help, it is a bit old, but it works and it will give you out the needed belt length 
@vishal_tejwani sent me more nfo in PM…
The motor pulley is 15mm wide and you will run single drive, so 15mm belt width would be my prority the wider the belt the longer life…
You will be using this motor mount…if i remember correctly it is made for 255mm belt on 15/36 setup…which would mean 61,46mm of center distance…from which I cn count that you will need belt with 58 or 59 teeth, the length would be 290 or 295mm…IDK which is better choice, the result is much closer to 290, but it is always better to go for longer than too short belt…the mount has changeable central distance so it should not be such a problem
I must warn you that the both the calculators are telling me, that you will have too little contact teeth on the motor pulley…
The best thing you can do is ask the seller of the motor mount to tell you the central distance (if you have it, you can messure it) and then decide if you cant do this I would go for 290mm HTD5 15mm wide belt
EDIT: acording to the pictures of the motor mount from the link, the central distance is bigger than 61.46mm…but there is no specific value 
EDIT2: The central distance is about 72.5mm (based on the specs of the same mount which is sold on by diyeboard…)…that means 315mm long belt Ask the vendor or measure the central distance yourself, otherwise you wont be sure you are buying the right belt http://www.diyeboard.com/50mm-63mm-diameter-motor-mount-with-drive-wheel-kit-1636t-5m-p-486.html
FINAL DECISION: 315mm HTD5 15mm wide belt
