This part is a bed-light lens for a 1976-1982 Plymouth Arrow pickup that is no longer in production and so I made it with calipers from a damaged original in TinkerCAD (https://www.tinkercad.com/things/2m4Mkd3qS7e-imasen-1189-200). It should also fit all the other names the truck was sold under. Plymouth Arrow, Mitsubishi L200, Chrysler D-50, Chrysler L200, Dodge D-50, Dodge Ram 50.
I have never made the molds, only printed the model in ABS (my printer just can't keep the mold parts on the bed without an enclosure).
This WIP design is for making a 2-part latex mold that will let you cast the final part in resin. Or you can just print the part in clear ABS like I did (mine was with a 0.6 nozzle and at 0.2 layer height with a 0.24 first layer).
3D print the 4 mold halves (a & b), then pour latex in each set. Use the latex molds those make to cast the final part in acrylic. If you can, use ABS to make the molds as that will let you vapor smooth them with acetone.
The final piece is in the designs as well as one that has sacrificial layer and built-in supports.
The sacrificial layer is to help the part stay stuck to the bed when printing in ABS.
The author hasn't provided the model origin yet.