Ramin:

I'm in Vancouver. 

The prices I'm getting are not for anything super special. But I'm only starting to ask around as was waiting for a 991.2 allocation and did not end up with one. So considering keeping the 3.8L for life and having some fun with it. Maybe a 4.0L with about 500 hp. But would need to be very reliable. I semi-daily this car and drive it to and from the track. Like, factory reliable [minus the engine fires, backed out bolts, coolant lines...  ].

Was under the impression that Rothsport was mostly air-cooled. Visited them one in my 930 days and they were very nice. Dundon is sort of local to me. But I don't know anyone with first hand experience with them. 

just buy a used turbo engine for around 25k, with some experienced shop exchange them and you have a 500 hp with reliability and modern car. people go for 3.8 or 4 mainly on air-cooled cars to gain 60-90 hp .and cost easily carries between 40 to 120k. suggest you read some of the builds at reenlist, Trophy or Juha