Hi, I've still got the original Dormi sales leaflet for my '70 (v v tatty) and it doesn't mention tyre pressure however I've checked the 'Instruction Manual' and it states:
for front (ambulance/ microbus l/ microbus and all other models): 28psi (2.0kg/cm2)
rear - to 3/4 payload (ambulance/ microbus l): 28psi (2.0kg/cm2)
rear - to 3/4 payload (microbus and all other models): 35psi (2.5kg/cm2)
rear with full payload: ambulance: 28psi
rear with full payload: microbus l: 35psi
rear with full payload

microbus and all other models): 41psi (2.9kg/cm2)
Note also that for prolonged high speed driving, increase the pressure by 3psi (0.2 kg/cm2)
Hope that's clear!