Hey,
It sounds like a cool idea. From what I see I'd say in the $1500-$5k range.I've seen some decent looking ones around $3500, unfortunately they are very sporadic,I don't see many 71-73's anymore and when I do they are usually fastbacks and verts. One of my many car regrets was not buying a 72 Grande.I remember I was in college and I had just bought a beater 73 Capri for $50. Anyhow I go to this shop upstate with a friend and they had a gorgeous 68 Cobra Jet they were working on,out front they had this Grande,it was about a 20 footer, 302 ,auto,A/C,Disc brakes,ran really well. $250. That would have been a great driver. Anyhow Good luck on your search. I'll keep my eyes open for you,if you'd like?