Juswt a bit of history...
Before the M1A was introduced (the Devine, TX rifles) you couldn't get M1As. Even M1s were limited to either 1 DCM rifle per lifetime or an M1 made with a rewelded receiver.
Some guys who had the cut M1 receivers modified them extensively and rewelded them into interesting M14 type receivers but it left you with, guess what? A rewelded rifle. Lotsa work, but it was all you could get. And rare at that.
Later Springfield Armory Inc offered rifles and receivers. They were a better deal, but with cast instead of machined receivers. They've served well.
I'd really recommend you don't bother cutting and welding an M1 receiver. Sell it and get a Springfield receiver. If you have about $300 more to spend you can get an LRB receiver that's machined from a forging. They're beautiful receivers.