I can't comment on the 270 WSM conversion having not actually built one. The Ruger however is one I have done several times. It can be done on a vz24 but I have built the majority on commercial actions mostly Zastavas. Start with a short magnum action (7mm Rem or .300 Winnie) and the bolt face is already the proper size and the feeding work required will be minimized.

I built my 416 Ruger off a Zastava using a .30-06 action.

The Ruger conversion is to be preferred to conversion to H&H length cartridges to be sure. MUCH less expensive to boot.