"Car is smogged and will be registered before sale." --> Here is the 'red flag' for me.
This says to me that it was previously not registered or a 'planned non-op' car. I'm curious as to how this car passed the CA smog visual inspection.
Personally, I wouldn't buy a modded Subaru in CA without the OEM (turbo back) exhaust as part of the deal (so that I could pass future CA smog visual inspections without having to bribe anyone).
70 to engine rebuild faster than you can say "poofff!"