I need an opinion on an engine swap

[Flightman91]

Not sure if this is the right spot for this. Feel free to move.

So I'm tired of having my trucking drinking gas like its going out of style (8mpg). In my quest to make my truck more driveable I'm looking for better MPGs. Right now I'm running a 1973 390 with a 2 barrel carb, single exhaust that is 3" till you get to the muffler then is 2". I have an NP435 with divorced Dana 24 and 3.77 gears on the back which will be becoming 4.10's all around. I've been thinking about swapping in a Cummins and I'm not sure how far to take it. So I'm looking for suggestions. I'm not sure if I want to put in a manual or automatic. And I'm on the fence about what to do with my T-case, which I just put new bushings on. I'm looking for cost effectiveness too. So I figured ask the people who have been there. Please give me your opinion and reasoning behind it.

[Ranchero50]

I did and would do it again. Been driving mine for about a month now and am very happy with the results. There are a couple Cummins builds in the projects sub-forum. I'd suggest reading up on them and seeing what parts you can find.

I chose a VE rotary pumped engine from a '93 Dodge and a 47rh transmission from a '94 Dodge over the A518 AOD transmission my motor came with. The 47rh has a lock up torque converter which makes the transmission act like a manual and also makes it run much cooler. I'm also running 3.50 gears and think 4.10 would be too high unless you were running very large tires. The 6bt wants to lug, not rev.