Some high-end boat, horse and race trailers had vacuum-over-hydraulic brakes for a few years. MasterBrake of Dallas sold a bunch of the systems to trailer manufacturers. MasterBrake sold out or went bankrupt, and about all that's left is their BrakeSmart electric-over-hydraulic brake controller now sold by someone else.
To prepare your truck to hook up to a trailer that has vacuum-over-hydraulic brakes, you need two main things. First is a much-bigger vacuum pump than the one that came on your truck. And next is a trailer brake controller designed specifically for vacuum over hydraulic brakes.
I'd find a high-end trailer manufacturer or retailer and ask where to find the vacuum pump and brake controller required for your trailer. One such outfit with optional vacuum-over-hydrailic brakes on some of their trailers is Texas Bragg Trailers in east Texas.
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Or you could contact the manufacturer of your trailer. Or better yet, the manufacturer of the brake system on your trailer.
