I have been watching this guy's build series and it's pretty good. He also has an RRC that someone did a camper conversion on, a manual D1, and other Land Rovers.

 

I've been watching him too, he did the exact swap I want to do, aluminum LM4. Can't wait to see what he comes up with for the intake, get rid of that flex hose.
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Gas mileage was terrible though worse than my 4.6

 

I have the LM4 too - its a nice engine. Definitely the best option for the price / performance / weight. This is what I did for the intake. It was made from a bunch of random parts, but it's worked good since I made it.



He was running 35s with stock gears, which has a sizable impact. He also said he was pushing it during the shakedown run. I've seen around 15 with mine at times. Similar setup with the Rover V8 was getting around 11. Just having a standard Silverado tune will affect it a lot as well - you can get better mileage if you have a tuner optimize it for 4WD. I wouldn't be surprised if it improves a bit for him as well.