Need an internal door thats 77"

Hi there,

Due to sloping floor i needed to create a horizontal threshold for my bathroom door (old house....). Now this is done i need a non standard height of about 77". Could this be achieved by buying a standard door and planing off an inch? In my limited experiance this can't be done with a moulded door so what sort should i get and anyone know of who would sell one? Very frustrating!

Thanks in advance