If all you want the brake for is to warm the cab quicker in the winter you could save a bunch by just installing a butterfly flapper in the exhaust elbow that you could close with a cable.
You can wire any of the exhaust brakes to work manually by just installing one switch in the power to the soleniod and eliminating the ecm or throttle switching.
You can wire any of the exhaust brakes to work manually by just installing one switch in the power to the soleniod and eliminating the ecm or throttle switching.