I will give you what I believe is the belt routing.
For the future (and also if you find my info wrong), remember these rear finishing mowers, painted orange, are made by Landpride which is now owned by Kubota
On the Kubota Canada web site they list 3 mowers. Models FDR 1648, 1660, & 1672.
All three have the same belt routing.
If you go on the Landpride web site you will recognize your mower and find the manual for it.
If you now have a new belt ( for measurement purposes) and want to learn how to buy high quality but much cheaper belts please ask.
Landpride.com
There is a second heavier series of mowers made by Landpride and I have included the belt routing also
Dave