My 401a weighs 22 pounds while a 301 weighs in at slightly over 16 pounds. The Singer 401a and 301 are both slant shank machines which means their feet are interchangeable if that's a consideration. Many of the other vintage Singers (e.g. 66, 99, 201)are low shank machines which means their feet are not interchangeable with the 401 or 301. As Patrice indicated replacement feet are cheap. It might also help to google any vintage Singer model you are considering to learn more about the machine's features (e.g. straight vs. zig zag capabilities, etc.)
Here's a link showing which machine models have feet that would be interchangeable with your 401a:
https://www.sewingpartsonline.com/st...ant-shank.aspx