I have a couple of Tonka trucks I've dolled up with various accessories. As they come from the store, they're just the body and wheels, no interior to speak of, no running gear or engine. Perfect for Little Johnny to abuse in the sandbox, but not much from a "model" standpoint.
I found a print file for a Cummins 5.9 and thought "That'd make a perfect engine for the Tonka!"
Downloaded it, resized it to rough 1:16 scale, sliced it and added supports so the overhanging bits would print properly and popped the results in the printer. Projected print time: 10 hours!!!
This is what it looked like as it came off the print bed with all the supports in place. Removing them was a project in itself.
This is what it looks like with the supports mostly removed. Some more cleanup to do, but I'm impressed with the detail, right down to the injector lines. Should look great when painted!