carbs will never be as efficient as computer controlled fuel injection. It’s much harder to modify a vehicle with computerized fuel injection because a)they’re tuned to much finer specifications and b)the computer is set to look for a fine line of specifications and keep the engine operating within those specifications. To change anything you also have to change the specifications of the computer.
That said, I’ve owned several carb vehicles and several fuel injected vehicles and the fuel injected vehicles always ran much longer on less maintenance than the carbs. There’s a reason there’s no carbs on vehicles anymore and it has a lot to do with carbs simply being inferior technology. The only reason carbs are still around at all is because they are easy/cheap to work on.
There are also a lot of other engine differences between a newer truck and a vintage truck. Stuff like roller rockers and hydraulic lifters, cnc machining, etc. not to mention transmission differences.
the 2012 truck will easily outlast the 70s truck if it’s maintained properly. The problem is sometime down the road there’s going to be a major failure. With the 70s truck it’s simple enough to just drop an engine/trans out in your backyard and get the thing running again. Newer vehicles are much harder to tear down and rebuild like that (but it can still be done if you know what you’re doing). It’s not that the 70s truck is built that much better than the 2012 truck, it’s just that the technology progression of vehicles has advanced much faster than the average person’s learning curve. In 2027 when the truck is 15 years old and not worth much, lets say the transmission starts slipping and needs to be replaced/rebuilt. It’s gonna cost say 5k to get the trans fixed and the truck back on the road… but the truck is only worth 5k anyway… The only reason you would drop the cash for that repair is out of nostalgia. Otherwise it’s the better bet to just drop 5k on a new truck. When I was 17 I rebuilt the 289 out of my 70 mustang with a basic set of sockets and wrenches. No torque wrenches, no specialty sockets/bits, etc. It ran for 4 more years (about 57k miles) before the engine crapped out again. Heck, try to put an intake manifold on an engine today without a torque wrench… you’ll see what I’m talking about.
This is the reason most newer vehicles don’t last like older vehicles. Your average person simply doesn’t have the tools/knowledge to keep that 2012 truck on the road forever and eventually it’s just not worth it to fix it anymore.