I had many Betas in my day,
The belts were the same as the 2.0 fiat twin cam as far as I can rember
the 1.6 belt is 2 teeth shorter as I found out many years ago with sweat rolling down my brow
trying to make it fit !!!
Check the condition of the tensioner bearing, there's no point in changing the belt if it jams
you'l be picking bits of valve out of your exhaust,
Good luck with the car
David