All depending on how bad the car is at the beginning and the end goal in mind.

I could see some shops having well into 100k before a car is done. I know for a fact of at least one 1971 Challenger conv done by a shop in northern Ky ( NO not mine ) the man had well over 100k in it once done.
And this was 340 challenger conv clone from a 318 car. That required A LOT of metal work .
Painted a deep purple color , Similar to But dont think it was FC7