I've taken on the role of webmaster for the AACA Ilinois region and am a 3D printing advocate.
I've posted some articles on the Ilinois Region web site on 3D printing along with links to collections of 3D printable parts that have been posted to Thingiverse and Printables.
They are not well organized at this time, but they do collect many of the automotive parts posted to these sites.
Links to 3D printed parts - AACA Illinois Region
I am a retired software engineer with a background including graphic arts.
I post all of my designs free for others to use.
Because I do not have a 3D scanner, certain parts take multiple passes to get the geometry right, particularly if I do not have a viable sample to work from.
I personally have created the following parts (not all yet completed or posted on line)
Door sill plates for 1953 Chrysler Convertible. 42" long printed as one piece on a CR-30 - took 5 days.
Hood bumpers for 1936 Nash
Front and Rear bumper grommets for 1936 Nash
Shock absorber grommets for 1936 Nash
Fender plug for 1965 Caddy
Carb heater Dash panel 1927 Nash
I've had great success with TPU for soft parts and prefer ABS for hard parts.