To make a financial profit, you need to be able to write off your time - in other words time is what you are selling and that is what the buyer will be paying for. Don't expect to cover your time AND clear a profit. There is little profit on the parts and components unless you can strike a wholesale price deal with a manufacturer. That again would be dependent on establishing yourself as a volume customer or maybe convincing them that you will be getting their product some exposure and potential sales in a (geographic) market that they haven't penetrated. If you can put together a good (Ford) engine/transmission combo yourself and install it along with some minor assembly and body prep/paint, final assembly of a good "pallet kit" for customers might be an option. Bear in mind that most manufacturers already perform this service so you would either be competing against them or working with them as a licensed assembler.
For an inherently "correct" looking car with all the right stuff already included, you really should look at Unique Motorcars.
http://www.uniquemotorcars.com/Pages/kits.html
Their deluxe pallet kit is one of the best on the market and they are recognized as one of the oldest and best in the business. The Weavers ars first class people to deal with and their product is top notch. No fabrication - just straightforward assembly required. Good luck.
P.S. Don't overlook the suggestion about the Jag rearends - it's a good one.