I see your machine was probably one of those put together from parts, in Scotland I believe if I remember correctly. The hood and nose are the identifiers.
Over here most are using a Goodyear variable speed industrial belt. My machine is a few miles away in storage on another part of my farm. If no one else chimes in here I may go and look for the part number. In my opinion this belt is a good representative of the original part. If I remember correctly the angle of the face of the belt is 1 degree different than the originals. I found I had to retention the belt at first a few times as it wore in.
Regards, Kirk