Think I’ve had mine about 18 years this year and I’ve had just about every part off to replace / refurb
Rear floor, front floors , a posts, front panel, windows, rear door, both axles and diffs , all springs , seat box repair, engine refurb (2) , gearbox refurb , all brakes, fuel tanks.
Surprisingly I stopped saving all the receipts and doing spreadsheet of costs years ago it think it’s worth more than what I’ve spent on it in those years!
Bear in mind it won’t be just cost of chassis it will look so good you’ll want to change other bits , but if you refurb those bits first it helps also to get all the rusty bolts off so when you come to remove items for possible chassis change they’ll come off easy and won’t need to replaced
Other think to consider is the space available to strip/ store stuff in dry if poss.