What's the issue that would suggest this other part? A switching supply will still consume some power besides what it sends to the gauges. This will require a ground to function, just like the 7805.
This "DC-DC convertor" is a switching power supply. It takes the 12v DC input and chops it (turns on and off) into square wave AC at a high frequency. It then uses a transformer (inductor) to convert this high frequency AC to a lower voltage. The resulting lower voltage is rectified into DC. Switching supplies are efficient but make a lot of rf noise. The supply in your computer is a switching supply.
If your switching supply has 4 wires, two in and two out, I expect they must match polarity (no isolation). That means two of the wires are tied together as ground, and you have the same number of connections (3) as the linear regulator. The 7805 does need the addition of a capacitor on the input and the output. (You can probably leave out one or both the capacitors - read the datasheet.)
When you have a vehicle that's powered by a tiny battery (drone? model plane?), power must be used efficiently. A switching supply will be more efficient than a linear supply, ie less power lost as heat. The 7805 linear regulator throws away the excess voltage as heat. However, in a Jeep, this heat loss from linear conversion is not significant.
I don't see how a little switching supply brings much to this issue. The 7805 doesn't even get warm in this application. Driving two gauges should be something like a 50-100 mA load. Nearly nothing at this voltage. No fewer connections. I guarantee that a generic switching regulator from the Shenzhen marketplace will have a much shorter lifetime than the linear regulator 7805 in this application. The parts are easy to find and cheap too.
46c for a name-brand regulator (ON Semi was spun off from Motorola).
https://www.digikey.com/product-detail/ ... -ND/919333
2 capacitors at 42c each
https://www.digikey.com/product-detail/ ... -ND/286789
Prepay your order to Digikey (send them a check) and they will cover shipping. An honest $1.20 total plus tax.