Sporterized carbines from the past
Probably the best thing to do if you want a "sporterized" M-1 carbine is to shop for a Universal that was done at the factory that way. The early Universals are made mostly like the GI carbine. The easy way to tell is if the op rod has the GI style cocking handle and camway for the bolt lug. You can find sporterized versions of Universals latter flat stamped op rod, but I don't like those as if you ever need replacement op rod, recoil spring or have any gas issues, you can not address those problems with replacement GI parts. You can IF you get the early Universal as described.
The sporterized models mainly consisted of a modified design stock and handguard. Some of these have retaining ring designs different than a GI barrel band. Usually no sling swivel and a Uncle Mike's style sling stud will protrude from below the forward portion of the stock. A bit hard to describe, but you will know it when you see it.
I whole heartedly agree with the postings that suggest not altering a real GI manufactured M-1 carbine. And if you have some customized idea that is not satisfied by a Universal, or Plainfield, or Iver Johnson sporter, then buy a cheaper commercial copy GI version and do anything you want to it. Have fun!