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.
Yes, you're right that Rothsport is mainly Air-Cooled. But water-cooled and later air-cooled Mezgers are not very different.
This place is further South down the coast but a good reputation for watercooled builds:
https://www.bbiautosport.com/
Here is their link to a Mezger GT3 Cup engine build, but they should be able to make you something custom as well.
https://www.bbiautosport.com/blog/2017/8/24/2010-porsche-gt3-cup-38-liter-factory-engine-rebuild
Manthey would be a cool option, but I bet they are very expensive and I would prefer to get installation and in-car sign-off on the project, rather than just receive a motor in a crate from Germany ...
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18 GT3 Manual, 73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs), 06 EVO9 with track mods. Former: 16 Cayman GT4, 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550, 79 635CSi