Thanks for the in-depth feedback! You can rotate with the mouse-wheel or with Q/E while building. I think we were missing some polishing of the build-phase. This includes the "can't place item" sound and restarting from the already built car. Both good points which we wanted to implement but didn't manage time-wise.
Regarding the Physics-Engine, we switched to Rapier2D in the middle of the jam, because we noticed that physics joints are not handled correctly in the default engine. And we wanted the car to be a little bit flimsy. We could have just added all objects to a single rigid body, which worked, but that wasn't the flair we were going for.
You can try it easily to see what happens without Rapier2D, if you leave out the rapier_<something>.so / .dll file, and start the exe without it adjacent, then godot will use the default engine. And despite no other changes, car just falls apart. The pieces are only held together by the pinjoints, the parent is a Node2D which doesn't move with the car.
In godot physics the alternative was to have a rigid body as the parent of all of them, and the other parts be a child rigid bodies. But this caused some issues as well, as this isn't how Rigid bodies should be connected. So we spent a lot of time tweaking the initial approach, but the car kept exploding, and then we switched to Rapier2D. which worked much better.
The source code is available if you want to have a look: https://github.com/LiquidFun/Grandpas-Hill-Racer