Nick Tune is the guy to contact regarding sourcing a Subaru engine, he will also modify the loom for you.. I paid £750 for my 2.5 quad cam ( chocolate engine

!! ) from him 18 months ago. It arrived on a crate, along with the loom ( I didn't have the time, inclination or space to strip a donor car myself) I obviously changed the cambelt and all bearings along with a couple of other parts.. I read all about the head gasket issues, but took the view that in reality these engines are easy to work on and fairly cheap to buy, so if it did develope a problem later on I would address it then. It's done approx 3000 miles so far, with no issues, just lots of smiles... The power really does make the bus into a completely different vehicle. I'm running a AGT 5 speed box with 16 inch wheels, 225/55/16 rears, which is 3800rpm at 70 mph, ideally I would love to drop that down a few thousand rpm, but it still gives around 26 mpg on a decent run ( hight top Westfalia) .
I have also upgraded the front brakes to drilled/grooved discs and matched pads.. This really helps, the extra bite and heat disapation is very reassuring.
It's not a cheap conversation, done well it looks almost factory... I have no regrets doing mine.
Good luck.
2.5 Quad Cam Scooby engine . Westfalia California 1989