There will never be a definite split because both dealers and manufacturers will order specific option variants but if a customer happens to want that specification then they'll take over the factory order for that car - and conversely if a customer-specific car is ordered it may well be carried into production even if the customer cancels.

It's good economics for manufacturers to move away from "sell from stock" to "sell to order" and different brands have widely differing policies on this but factory lead times have generally extended as the industry has shed it's excess capacity.

My last two new cars have been built to order - a Vauxhall Astra in 2000 because of the option combination and a Hyundai Santa Fe in 2011 because of low stocks in the UK supply chain. Despite 6 weeks on a boat, the Hyundai was delivered in 10 weeks.

I recently bought a new car, and was told by the dealer that I had a limited choice of just a few colours. It took a couple of weeks to be transported to the dealers, and judging by the surface rust underneath, had been sitting in a yard for some time.

Most Japanese (and other Asian) cars are built to stock, rather than order because of the shipping times involved.

When I bought my MX-5 it was shipped from the Netherlands, which is where the central stock is held - so about 10 day lead time.