There's another point about scratch builds. Do it only if you're an experienced fabricator and willing to dedicate enormous amounts of time.
For most people there are also investments in tools and other items that you'll use only once. And most who have done it have or wish they had a lift.
Do it for the love of hands on work, not to save money.
You should read every topic here:
http://www.clubcobra.com/forums/scratch-builders-forum/
Good luck.