I did used to oooh and aaah over the .38 super when I was a kid reading my Uncle's old "Gun Digests". On paper, it's pretty close to .357 magnum so long as you don't wanna shoot heavy bullets on pigs or such. I think I'd pick it over the .357 Sig, personally, except for carry. 1911s are mostly 40 ounce guns and .357 Sigs are on .40/9mm chassis. Of course, for hunting, why stop there. Move up to 10mm.....or, just do what I do now and pick an appropriate revolver. I'm certainly not allergic to revolvers and they're more accurate in general and totally more powerful.
As to the conversion, I have no clue. Sorry.