Does anyone know what it would take to rechamber a 375 Dakota barrel to 375 Ruger? Does the barrel have to be set back?

. Prolly need set back quite a bit !! You may need a new barrel ....... Have you thot about the 375 AR . Or a simular wildcat using 404 brass ???

Yep, need a new barrel for that.
The .375 Dakota is the fatter case of the two, it is a ".375/404 Jeffery Short," a more powerful cartridge than the .375 Ruger.

Thanks for the help. I haven't bought the rifle yet but just looking at the cost to shoot the 375 Dakota. The difference in cost of dies and brass would pay for a rebarrel pretty quickly. Probably wouldn't properly feed the smaller case though?

It might feed .375 Ruger better than it feeds .375 Dakota.
However the boltface is bigger on the .375 Dakota.
You cannot add metal to the boltface, unless you are a magician.
Need a new bolt and a new barrel ... unless about 10 thou of "extra slop" works O.K.
That might be too much.

A .375 Dakota ... .375/404 Jeffery Short ... is not that much more expensive to feed than a .375 Ruger. Dies and brass, and the brass will last a long time if you don't hotrod it.

Found out the dies and some brass are included . . . going to take a look tomorrow. Anyone have 375 Dakota load data?

Go to
http://www.accuratereloading.com/reload.html

and select the .375 Dakota:

http://www.accuratereloading.com/375d.html

Better than a .375 Ruger, just less common nowadays.
375 Dakota:

Reckon the specs for Saeed's .375/404 Jeffery Long
are same as the .375 Dakota (2.570" case) except lengthened to 2.850" case length?

Still top secret.