Modify & Engineer CAD Drawings For Car Platforms

We have CAD drawings for 2 different sizes of car platforms (30 inch tall and 36 inch tall) that were created for us by a designer/engineer in Solidworks. We like the overall design, however, the drawings were created with the intention of producing the product in China, and thus, the materials chosen and measurements are in metric. We need the measurements and materials to be changed to North American standards and need the plans to be engineered/reduced in weight substantially to reduce the cost of manufacturing. This project entails the following: 1. Evaluate overall design and look for areas of improvement with respect to safety and reducing production costs. Evaluate if our goals are achievable. 2. Change all measurements to inches from mm. 3. Change all material choices to standard angle iron and tubing materials available in North America 4. Reduce overall weight of both units, while maintaining safety. The 30 inch platform currently weighs 792 pounds and the 36 inch platform weighs 848 pounds. We would like to reduce the 30 inch platform to 700lbs or less and the 36 inch platform to 775lbs or less. The less weight, the better as long as it is safe. 5. Evaluate the plans and determine what weight of automobile will be able to be safely supported by these platforms. The person we hire must be familiar with angle iron and steel tubing that is standard in North America and must understand basic steel/welding manufacturing practices so they can look for areas of improvement that will reduce costs. The person must have a very strong engineering background and be able to accurately determine how much weight these can support and be able to find areas to remove unnecessary steel and labor to save costs. If this project is successful, we are looking for an engineer/designer to work with us on a long-term basis to develop many more products with.