Here is a parts list for DIY'ers who want to convert a Aircooled (80-83.5) or Watercooled (83.5-91) Vanagon to Subaru power. I've supplied these part number but do your due diligence to make sure they'll fit your application. I've had great luck with these parts myself. Enjoy the build!

Below are affiliate links which help provide more great content for free - I know it doesn't seem like much but it really helps out using the links - much appreciated!

Vanagon Conversion Parts List: Approx. Pricing  
KEP Manual/Auto Transmission adapter kit, Exhaust Header (dual-port), Catalytic converter and welded Muffler assembly, Muffler Bracket, Crossmember $1,500 Must order over the phone
"Single-Port" exhaust Market
BUSARU Wiring Harness Conversion $899 BUSARU Harness Conversion
Rubber Coolant Hoses for stock radiator 1 $9 Hose 1
Rubber Coolant Hoses for stock radiator 2 ??? Most places are out of stock
Stainless Coolant Pipes $310 Stainless Pipes
Vanagon Radiator $149 Radiator
Coolant Pressure Bottle, Level Sensor, Cap $20 Stock Replacement Bottle , Level Sensor , Cap
Clutch Kit $127 Clutch Kit
Optional for Aircooled: Large heater assembly (For Under Rear Seat) $185 Large Heater
Optional: Shortened Subaru Oil Pan $270 Must order over the phone. You can see video of me installing on the BUGaru HERE and on my personal bus HERE
Alternator Belt $19 Alternator Belt
Optional: OBD2 Gauges/Adapter $100 OBD2 Gauges/Reader
6 Port Fuse Holder $10 6 Port Fuse Holder
Universal Intake, has enough bends to play with $73 DIY Intake Setup
Aftermarket Fuel Pump (Stock FP works great) $80 Inline Fuel Pump