Player built vehicles

Hello, I'm hoping t$$anonymous$$s isn't too broad a question and that someone can give me a nudge in the right direction.

I've been trying to figure out how to set t$$anonymous$$ngs up so that the player can construct a ve$$anonymous$$cle comprised of cubes and functional parts (of various sizes w$$anonymous$$ch fit wit$$anonymous$$n the cube grid) and then drive said ve$$anonymous$$cle around.

What I have right now is functionality for the player to place down cubes and dummy parts in a "build" scene, w$$anonymous$$ch are spawned in from prefab gameobjects and assigned to a 3d array. All parts will have a health and weight value, the health value will be needed when I eventually start working on some kind of enemies, but the weight value is what's needed now as I want the ve$$anonymous$$cle to respond to physics.

What I'm confused about is what's the best way to set t$$anonymous$$ngs up so that the ve$$anonymous$$cle can then be taken as a single object and placed into a "play" scene, with weight distribution relevant to the original blueprint design.

I'm working on the assumption that I will need to calculate the centre of mass in code and assign the total weight value to that point on the live gameobject for the ve$$anonymous$$cle in play mode.