The only reason i'd question that one being 540 rpm is that it looks fairly old. Alot of older machines have multi-speed PTOs..... so it could be concievable it could be designed for a 1000 rpm pto. Unlikely, but possible. FWIW, six beans is relatively short money for a blower..... even though it could use a dressing up.
I figured i might get in trouble for using the h e double hockey sticks word.