I have always used X acto, I have one that I've had for years and it's lightweight and fits my hand well, and I just like the way it feels, but that's just my preference!
I like the story especially you and your Dad doing that together, the models still look great to be that old great job preserving them I know they must an awful lot to you, thanks for sharing!!
I like it, (IMO) I would go with the duel wheels it will give it that beefy look especially since it's going to be hauling a race car, looking forward to more!!
I just saw that same rig about 2 wks ago pass me on the highway, George is that the Biltmore Estate? wouldn't want to have to pay for a buggy full of groceries in that one!!!