Im wondering how much it would cost and what id need and any mods needed to swap my 1990 D250 Cummins to a 1990 W250. Ik people have done it but wanna see if its something ID wanna do

 

The cheapest way is to buy a roachy cummins W250 for parts. That way you get *all* the necessary pieces. Sell the leftovers to reduce your overall cost. A rolling chassis isn't a bad idea either... but then you're often left trying to chase down the right trans & tcase, and possibly driveshafts.

The 91.5-93 diesel frames are beefy - 2" taller. The 89-91 autos have the 3.07 axles that are tough (near impossible?) to re-gear to anything else.

Hope that helps...

 

The 91.5 still had the lighter frame. I know, I had one. I wouldn't call them weak. In my wreck, even though the frame "racked", it didn't bend. It also stood up to the weight of a loaded 35' fifth wheel.
Getting a donor is about the only option anymore, the surplus parts pool is empty. And there are a lot of parts involve in the swap you never think of until you're there.

 

Looks like the OP is in Mass. which means is is close to a "surplus parts pool" as you put it for parts.

I could supply him with any to all of the parts for this swap.

4x4 Frames, which could include all the 4x4 suspension and an axle [s] if needed.
I also have many 4x4 transmission and t-case options.
Any 1st gen driveshaft someone could need.

I have enough stuff here to do a 2wd to 4x4 swap on 4 Cummins powered 1st gen trucks without having to leave the shop to search for parts.

 

Interesting. The 91.5 I wrecked out was the 8" frame. Intercooled, clubcab, and mexican production (if that makes a difference). Seems there's no definite time the 8" frame took over on the diesels. Yet, there were 6" w250 frames (gas) thru '93.

 

They didn’t make any Diesel club cabs until 1992. I’ve owned at least two 91.5 W250’s and they both had the 6” frame. I had 2 91.0 W350 SRW’s however, And they were both the tall frame. I’ve owned about 14 91-93 W250’s and everything 92 and newer has had the tall frame.

 

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Production date was May '91 on that clubcab.

Wherever dodge split it up... I'd shop around for the bigger frame if changing it.