Ok, no love for retrofitting
How about this part from Wikipedia:
"he first system, called ACT-4 (active torque split) by Subaru, was the same setup commonly found on other Subaru models of the period, and used a variable clutch pack center differential using a 90/10 power split ratio front to rear, which could transfer up to a 50/50 power split ratio for maximum traction if the front wheels started to slip. This AWD system was offered throughout the entire production run, and was used in vehicles manufactured for sale in the US, Canada, Germany, France and Switzerland. A sportier continuous traction delivery system, called VTD (variable torque distribution) by Subaru, was used in vehicles for sale in Japan, the UK, the Benelux region, Sweden, Australia, Spain, Austria and Brazil. The VTD AWD system is a permanent AWD due to its 36/64 split.[7]"
Since I'm in Europe I can probably shop around for desirables. Any thoughts about pros and cons on the AWD-subsystem? Apparently VTD sounds better but I only think that because it's "sportier". I understand this system has a rear wheel drive bias?
Any thoughts about what provides better traction?