If you have a shop and a business with staff and overhead, then the hourly rate should be what it is. The customer should have a realistic idea of time involved upfront, or they might flip at the 2k invoice.. Obviously, there are some uknowns, but they should at least have a window of possibilities. If you do this stuff on the side in your garage or theirs, I don't think you can ask the same rate. There is also some risk on the customer side as to recourse if something goes wrong with the job. That being said, complete front end rebuild is a lot of work. With all the issues that can arise with 50 year seized up parts, who knows... There are so many variables