XPostFacto from what I hear can get OSX on older machines like the 1400. But its a major headache do it on a 1400 from what I hear, though I wonder if this is with or without the G3 upgrade. The 1400 is not on their support list, but from looking at the support list, it is using "Stock-Non Modified" machines. So who knows.

http://eshop.macsales.com/OSXCenter/XPostFacto/

http://eshop.macsales.com/OSXCenter/XPostFacto/Framework.cfm

https://eshop.macsales.com/OSXCenter/XPostFacto/Framework.cfm?page=Compatibility.html

https://eshop.macsales.com/OSXCenter/XPostFacto/Framework.cfm?page=XPostFacto3.html    <-- For Download Links and FAQ

OS9 Helper should help get OS 9.22 on a 1400:

https://eshop.macsales.com/OSXCenter/OS9Helper/Framework.cfm?topic=32  (click icon to download)

http://www.os9forever.com/Compatibility.html  <-- compatibility list, though it just hung there and then failed to connect for me.