Being in the service industry I totally understand that it seems as times that you just can't make anyone happy sometimes. But, I will tell you what I have learned though the years that might help you here. Even though it may not be what your customer wants to hear, it is ALWAYS the best policy to over communicate what is going on. This is especially true if you aren't going to be able to deliver on time.
We all understand that you depend on your leather supplier to complete orders. Or waiting on Ford to come up with build #'s. Or whatever. It is supper important for your continued success around here to communicate with us on a more regular basis. I haven't got my product yet, but based on what others say, you do a great job at a fair price. But it is just as important to take care of these communication issues so we will all continue supporting you and passing your name onto others.
I think just a short, daily update on this thread with how things are progressing would stave off a lot of the issues right now. If it's a real problem, then a PM is the way to go. Either way you go, you should spend just a few minutes each day updating all of your current customers and future customers will see those conversations and believe you will be there for them......