the 500 Jeffery fits in a standard 98 action, but I do not consider it the best solution.
My dear friend Fritz has a 500 Jeffery from Reimer Johannsen biuildt on a magnum action, feeding is perfect, and the cartrige can be used with the 570grs Woddleigh bullets crimping groove.
Mr. Hirschle in Blaubeuren/Bavaria is producing 500 Jeffery rifles on modified standard-length 98 systems, and the two rifles I could examine fed standard cartridges (535grs RN SP and FMJ) also without problem.
If cost is not to be considered; I would recommend a magnum system for more weight in the system area and therefore better handling.