This is a gear shifter I made in Tinkercad for my 1974 GMC K20 I have. It is designed to pause the print about an inch up and fit a 14 mm nut inside the model and continue the print. Once its done it simply threads onto your stick! Make sure before you put the nut in the print that it will actually thread onto your gear shifter lever!
There is a file that is a 4 speed sm465 pattern set up, but i included a 5 speed version as well for later models.

See my Chevy Shifter design here! https://www.thingiverse.com/thing:4286189/files

Yes

Yes

25-50%

Paint the numbers a different color to stand out as you cannot do a simple fillament change on this design.

Pause the print and insert a metric 14mm nut into the hole and continue printing. If it doesn't fit right, file off some of the nut to get it snug. .