I just lifted my truck and put a set of 35x12.50 tires on my 1990
Dodge 1/2 ton 4x4, automatic with overdrive, and the 318 engine. I was wondering what would be the most realistic gear size, I drive on the road during the week and four wheel on the weekends. I was thinking a set of 4.56 gears but would a set of 4.10s be more realistic?

Thanks,
-Eric  

Hey sugarkid! If you watch "Trucks TV" on TNN, the host put together an early Bronco ("Crazy Horse") with a six speed, 35's and a 4.56:1 rear gear. That truck was amazing! I'm guessing since you spent a lot of time and money on your ride, you intended it for having a lot of fun with it 4.56's would be  fun but not be too impractical. If that's the case, GO WITH THE 4.56:1's!!! If you drive it a lot, like mind-numbing 45 min plus commutes and want an truck that'll get excellent mileage go with the 4.11's. With the 4.11's and 35's, you're first gear will be similar to a Town Car, Crown Vic or a base-model pickup. It'd be like ordering 3.42 gears with 235/75R 15 tires. (your basic 80's and early 90's 2wd pickup) With the 4.56's though, it'd be like getting 3.81's with the stock tires. Without the overdrive at 80mph, you'd be at 3530 RPM and at 70mph you'd be at 3090 RPM.  BUT YOU HAVE OVERDRIVE. With a 25% (just an example) overdrive that's only 2649 RPM at 80mph! GM's overdrive is around 30%. If you have a good overdrive like 25% or more, you could go 80mph at 2835 RPM on 4.88's or! If you're overdrive is 30% or more you might still think 4.56's are a little slow in 2wd or 4 Hi. If it were my truck with overdrive, and I didn't need to put several hundred miles on it every week, I might look into 4.88's instead.

P.S. Do you do rock crawling or mud and sand? If you like going fast, 4.56's will be better; 4.88's if you 'wheel  not so fast. 

What stock gears do you have? I had 3.73s and did ok with 35's, but I swapped for 4.56's and am very happy.  Still accelerated and pulls hard even in 5th gear at freeway speeds.  Try randy's ring and pinion's website, they have gear ratio calculators that will help you decide what gears will meet your needs.