Extension Cord For 220 Welder

I've almost always chosen to err conservatively, and go with bigger wire than strictly adequate. If I read correctly, 25 feet is the longest pre-made cord anyone who has replied yet is using. I would talk to the local welding supply folks. I would probably go with 10-8 for 40 feet. However, I would try to move that 220 outlet closer first.

ATB BC