Actually, leather is an excellent gasket material for certain applications,
Pro's- It's very tolerant of less than perfect seal surfaces, abrasion resistant, and is relatively unaffected by UV light. If it's treated correctly it is long lasting, and it can be impregnated with lubricant easily.
Con's- Dimensional uniformity can vary (It comes from cows...) , both finish and material properties can vary (It comes from cows...), limited availability and thickness limitations ( It comes from cows...)
Leather was almost certainly more expensive than paper or rubber back then, so If Ford thought leather was the best material for the job back then, I'd go with the leather today...
JMHO. John