I am pretty certain that the magazine box of a standard Model 98 trigger guard will be too short for a .404 Jeffery without modification. This would include commercial hinged TGs from the Interarms Mark X (.30-06 length) as well as military ones like the Argentine Model 1909 and Portuguese Model 1904 (8x57 length).
Unless Steve's Oberndorf TG is long enough, your best bet for a factory hinged TG for a .404 Jeffery would be from an Interarms "Whitworth" Mark X in .375 H&H or a corresponding Remington 798 (both made by Zastava). Most of these have the side button floorplate release (mentioned by LRF) but some early ones had the release latch inside the trigger bow.
The other factor to consider is whether your stock is inlet for a "long" front tang (as used on most military Model 98s with a lock screw) or a "short" one used on many post-WW2 commercial rifles (like the FN and Mark X).
Last edited by Peconga; 10/30/12 02:20 AM.