[mike monde]

Why buy something else?
Unless I’m missing something,(rust) your car looks pretty cool
as is..with a few tweaks your car is well on its way on being what you describe...one of the coolest Rally/RGruppe type 911 hot rods that I know is a 912/6....rebuild the 6 and drop it in when its done...not sure of the number of building a hot motor but you live in Cali so there are plenty of great shops that could help you out there...if it where me? I would drive the car during the rebuild. Put the 912 engine on the shelf or sell to offset costs. Do some mild suspension work that reflects the type of driving you plan on doing.
Do the interior period correct with a rally theme and you will check that box..
Paint? Current color looks decent and if your going to drive it, save the money. Paint the car when it makes sense.
Create what you want piece by piece by keeping the car drivable seems like a good option.
Building what you want is more fun then buying someone else's vision IMO.
Have fun and enjoy the build..