With the few that I have done, the caster usually will tell you what to use for a donor kit. They usually have modified a basic kit into a model that has not been kitted. The donor kit will give you an interior and chassis that can be easily modified to create what ever the resin caster is offering. The windows are almost always a problem if the kits "glass" is different. Some casters will include a formed windshield and or rear window. Many here have used various clear plastics with great success. I tend to use the plastic that dress shirt makers use to keep a shirt collars shape in packaging. The plastic is very thin with no distortion and easily bent to match the curvature of a window. Follow the instructions on cleaning the casting before an work begins. When sanding, and there will be some sanding, you might want to do this away from you building area, The resin dust can interfere with painting as you move thru the build. It is also a good idea to wear a small dust mask if you have any respiratory issues with dust, this stuff can be very irritating. It really doesn't take that much extra effort to use a casting and if someone has an offering that you like then you should do one and just see how much fun they can be. Hope this will help.