best bet matey, it's not that rare in the UK now.
You'll need to sort the details with DVLA, which may be PITA, but worth doing so no issues down the line
neither of my engines have been and they have both been crackers. As you say opinions seem to vary on whats right and wrong, my advice is go with what your builder says.
2.5 will be drive by wire so loom is different. You can swap the bottom ends but then your looking at alot of making sure things match, like head gasket thickness etc. Very good mod, but def a case of best to build/spec from crank up, mismatched parts and it will be crap.
Also standard 2.5 its pretty !Removed! and suffers from head gasket and ring land failure. Built right they are prob the best subaru engine you can get though
I had an sc46 on my forged 2.5 hawk and would be my personal choice, prob come in around 460-480 but mega punchy which would be better to drive than a 500bhp car on the road.
was on low boost
only issue at the min is exchange rate means prices once landed are dreadfull, Decent type r is currently about 14k landed :o
From what i gather they are now at the age in japan where the rule change regarding the shaken (their MOT but alot stricter) so they are alot easier to keep on the road so becoming popular again add that to the exchange rate and no more bargins :(
Glad i got mine when i did.