I use the .375 Ruger cases for the .280 Ross since they were availlable. I even used the .375 RUM but this was a lot of work, as you have to turn the cases to makes them fit the .280. While I don't have problems reforming thoses cases, some seems to experience difficulties. So, stay away from the Basics if you can and use the standard .375 Ruger cases.
Woodleigh and Hawks .287" bullets are those easily encountered in Canada.
I personally used to shoot (and still have agood supply of) the Buffalo Arms .287" but now they're not availlable to us (not directly, though).
Kynoch ammo is Berdan primed, but yes, there is still a good supply of loaded rounds in Canada (for some time to go, not too long!). Those availlable are loaded with .284" bullets and don't shoot well in some rifles. Also, most of these Berdan primers are corrosive (less than most surplus, but still corrosive).
While I agree that D&T does not make it a totally original piece, it still carries the full lenght barrel and with little work, a good gunsmith can make those filled holes almost disappear, blending them to the receiver. So the D&T holes, as value goes, only lowers the price to a certain extent (the price the gunsmith will charger to get the job done).
To my POV, what brings the price down is the absence of the Porter peep sight. Of course, if the rifle is in good working shape, with plenty of rifling left.