Grab a clipboard.

Write down your budget

Start pricing what you know you want.

Disc conversion ( your stock wheels won't fit over the rotors )
Used wheels, New tires

Engine/ trans ( buy a complete vehicle, maybe something that's been wrecked)
Suspension parts ( consider the donor vehicle carefully )
Tools/equipment ( you'll need a hydraulic flare tool for that disc conversion)
Interior ( you doing it, or farming it out?)
Take the total, times it by %20 and add it together(conservatively)

If the numbers don't jive, then you've got some thinking to do.