David,
For a budget oriented car I think xl8or has come up with an excellent plan
that eliminates a lot of your labor and gives the customer a little wider
range of choices for options. Should make the out the door time much
faster with the different phases boxed seperately. The key here is concise
instructions for the assembly of these sub components so there are no
grey areas. Should also help your cash flow since you won't be providing
everything + fewer ordering headaches.