A good friend of mine is running a Subaru turbo engine and 5 speed Subaru gearbox (Subarugears conversion) in his 15 window T1 and i've never ever driven a bus before with such great driveability and low end torque (he's running a 175hp Forrester engine) as his.
My 1967 SO42 is currently running a 1776 type1 engine (witch is on his last legs) and the plan is to replace is with a standard 120pk NA EJ20 engine and KDFi injection.
There are more and more 'hardcore' aircooled VW drivers (friends of Wally and me) who are considering an Subaru swap for their VW's (beetles, buses and type3's) mainly for the reliability and the power to $/euro ratio