Bryan Cather has it right on the button regarding vintage car
restoration [130331 MMDigest].  One Duesenberg Model J had a badly
cracked head between every set of exhaust valves; it had obviously
seriously overheated several times.

The customer was notified, dozens of photographs taken and the decision
was left to the customer: weld it up and risk it happening all over
again, or supply a brand new head at $44,000.00.  He chose a new head.

The only sane way when restoring a complex device or instrument is to
charge enough down payment to cover the supplies, then submit a monthly
bill with a written report and photos.  Then there are no surprises or
harsh words.

Jim Crank