has any one ever converted a 2wd frame to 4wd, it sure looks like it would be relatively easy, I have all the parts needed off of a 4wd frame. my 2wd d350 crew cab long bed would be more useable as a 4 wd. the holes for the front mounts for the front springs are already there so that would position the front axle, would just have to drill the holes for the front spring shackle bracket.

Been done several times. Do a search. Its been discussed on here a couple times

I investigated doing it & basically you make a template using the original 4WD frame & bolt it to the 2wd at the bumper holes & where the prop valve mounts & start drilling
Good luck
Your CrewCab should have a 7 almost 8" frame so you will need to make sure your height is correct on some holes if you use a smaller frame for a template

found the other posts, thank you.