You mean the tube frame you've made? Piece o' cake.
Start with photos: a top down and one from the side (only one side image is needed assuming the frame is symmetrical). Hold the camera parallel to the floor for the top down, and parallel to the car's longitudinal axis for the side profile and hold the camera as far away from the car as possible without loosing too much clarity or making the image too grainy. Also make the frame (the very part you're modeling) appear at the exact center of the photos. Doing this will minimize distortion in the image and you'll create a more accurate model. Import the images into Fusion, place them appropriately in 3d space and use them to to aid in establishing the angles and intersect points for each of the frame tubes. Also, before you begin modeling, it's really helpful to establish a few control points in 3d space to anchor your model: mounting points, screw hole locations, etc. taken from the Tamiya parts.
It takes time but you can make a very accurate 3d representation of the physical model using this technique.
I've used a similar technique to create 3d models of bodies and other complex shapes.
Here is a Turbo Ultima body work in process. Since the body is so long, this can lead to a lot of distortion in a single image so I've taken a series of images (6 or 7 I guess), advancing the body about 2 inches between shots, then composite the images together.
The result is very little distortion in the final composite and I was able to reference the body lines in the photo to create a fairly accurate 3d model.
Hope this was helpful.