I never thought of it that way, but you're right. I do remember when Jack Lott worked on that one. The .404 case is very close to the .348 when blown out. Luckily the .348 brass is still made and easily obtained.
: I've considered building a rifle up for the same .458 Alaskan case necked to .375, but right now, the .375/06Imp that I've just put together is exceeding all expectations. 300gr. at 2,470 and 285gr. GS Speers at 2,560fps.& 235Speers at 2,845fps with very minimal load experimentation so far. Although the Improved .348 case would give another 17gr. capacity over the blown '06 case's 80gr., I'm feeling it isn't really necessary at this time.
: My desire was for a couple bear/moose thumpers & these will work splendidly.