From your post, I didn't really get the impression that this was the asking price ($37,500) but rather the "amount invested". If he has bought and sold other airplanes, then I would assume he knows to see what the market value is.
A couple of things you need to do. Get a list of the installed radio's and find out what "type" of major overhaul was done. Was it a field overhaul by the local A/P or to new limits or ??? I am guessing a field overhaul which does not enhance the value as much.
One other thing....the replacement with a 152 nose strut sounds fishy to me. You really need to carefully go over the logs, and see if there was damage. For instance...if the engine and prop were rebuilt at the same time the nose strut was replaced, it would kind of sound like she was made a one-off retractable for a day (i.e. crunched the nose gear).
If you are interested in this bird, approach the owner and say...okay...I am interested. What is your asking price? and may I start by going through your receipts and logbooks with my mechanic (you do have your OWN mechanic right?)?
If he gives you a $30K price....walk. If he balks on the logbooks....walk.
