I've welded a number of GM and Ford axles back when I had free access to the best metallurgical lab the Government could provide. The early and mid '60's GM axles I welded were determined to be equivalent to 1130 and 11018 D-2 as the most suitable rod. I forget what the Ford axles corresponded to but I do remember that 11018 D-2 was the reccommended stuff.
41xx is not a given for all high strength automotive applications as it's relatively expensive for general automotive use if something lower in cost is available. 1130 is a manganese steel not unlike that used in switch components for heavy rail traffic. It has good as forged strength, heat treats well to lower hardness like about Rc 35, and it's very tough and fatigue resistant. Metallurgically its more forgiving.
The weld prep prescibed for my axle welding adventures (I shortened maybe 50 sets) was a simple jig for alignment, J weld with runput tabs, upsetting the edge of the base metal to raise it above the as forged surface, root pass and grind back to sound metal, then alternate passes on each side to control distortion and to hold the axles straight and in alignment. Pre-heat to 450, interpass at 600 or less. Post-heat to 900 for 10 minutes and air cool. Grind off the run-out tabs and fair the weld into the base metal leaving a slight swelling. Hot forging was permitting to adjust length and correct offset and final straightness.
The point is if you don't know from actual tests what your welding when it comes to high strenght high confidence parts then you don't know what you're doing; you're gambling with the safety of the customer and anyone in the failure path should you be wrong.
My advice to anyone contemplating welding axles, front wheel spindles, and other high confidence parts is to pay the money and get the metal tested before you weld. Blithe assurances from ignorant but well meaning buddies (hey-ull I've welded a million of 'em and never had a problem) do you no good. Slick magazine articles written on bum research is worthless in the face of the need to have all the variables (material, process, filler metal, heat threatment, post welt testing, etc) nailed down in terms of numbers and hard knowledge.
Do it right the first time and you won't have to bury any mistakes or explain to the widow or the jury how Bubba said it was OK.