Ok so body work is way more expensive and then drive trains and it is best left to professionals. Now if you still must try this you have 2 options. You can find a donor car to remove it from which will require cutting up the other car or it will have to be hand made. This is some of the most demanding of metal fab projects and it has to be right or you will get leaks. I reccommend a hard pass on this one. You will find more issues farther down and on the floor. Not doing this right will get you rewarded with a twisted car as one of my customers that tried to do this to a 69 Z28 just found out after spending 60k on it when him and his son tried welding in a new floor with out properly bracing the rest of the body, one side would sit 1.5" higher than the other.
