Not to differ too much here....but I would get a fixed price because when he comes over and you are not working at his assumed pace or happen to be fooling with something while shootin the breeze with your buddy or having a cold one and not working at a break neck pace,he will assume you are screwin him over by only geting 45 mins worth of work done every 60 mins. With a fixed price you can take 10 hrs on the side mirror and no one complains.Take that long at a hourly deal and hes going to freak out.
The hourly thing gives them too big of a lever.......pro shop 55 bucks an hour and it takes them 2 hrs to set the rear end......your garage at 30 an hr and it takes 6 hrs,......see my point.The hourly deal gives them a lever to try and bust you down by saying it takes 110 dollars for the pros to do it and it took you 160 dollars to do the best you could.......see how things can get funky when you have a scale to be judged against.Say you asked 15,000 to do the job and a pro shop wants 35,000 you have a lever now by having a favorable scale to compare it too and bottom line no matter how much time is spent on each component you are still giving them a good deal.
This may not be the most profitable avenue to go down,but it keeps things from getting too far outa hand by having a base number for the restoration and no gauge on how long each step should take or cost ,only that it should be like this when complete....not how long it should take to complete or how much it takes to complete or whether you were working at a certain pace to complete.
This is what has worked for me in the construction field for many years,auto industry may be different,I dont know.