Lucas 14cux Hotwire setup is pretty self contained, and most of what you need is in the engine loom. There's about 4 wires to get it to run from memory. I have a Hotwire 3.9 in my early Range Rover that was previously carbs. You'll need a high pressure fuel pump and a return to the tank with a filter before the pump. Ideally the pump should be low down and near the tank but the one in the Range Rover seems to work ok on the inner wing. You need a permanent live to the ECU, an ignition switched live, a connection to the coil so the ecu knows the engine's running and a wire from the engine loom to feed the fuel pump. There's an ecu and a few relays to package somewhere safe and dry. Ideally you should have a speed signal from the speedo cable, but this isn't essential to get it to run. The Range Rover seems fine without this. If you connect this, the maximum speed will be limited. For safety, the fuel pump should be fed through an inertia switch. If the set up came from a car with catalytic converters, you'll need a different tune resistor to run without cats. There's a pin on the ecu loom to run a check engine light, maybe use the old choke light? There's also a pin that causes the revs to raise at idle. Useful on an auto so the engine doesn't stall when it's in gear, or for cars with AC.
In my Range Rover, the engine's really tractable. It will pull from almost stationary in 3rd, so long as there's some movement it's happy. Starts can be made in 2nd without the throttle just by letting the clutch up lightly. The ecu just adjusts the air bypass stop the engine stalling.