I have a flight box and a hardware (tackle) box. The hardware box has most of my building and repair/replacement items. If I need a screw, bolt, tail-wheel, etc. they are in the hardware box. I figure my planes are lighter than my hardware box, so that stays in the car most of the year and I carry my model to the car if it's needing repair.

Props, tape, glow-plugs, tach & ESV, tools, wheel collars, rags, cleaning solution, bug balm - those are things I might need in the pits so they are in the flight box.