The Eberspächer BA4 gas-electric heater that’s standard in Type 4s
The Bosch L-Jetronic (air flow controlled) fuel injection system which was used on the US-spec VW 412 in 1974
Other material of interest
Paul Anders’ site has some great D-Jetronic fuel injection information.
Russ Wolfe scanned the fuel injection pages from a VW workshop manual, they describe the D-Jetronic as used on the Type 4 and Type 3.
Another set of scans on Russ Wolfe’s site shows a automatic transmission troubleshooting guide.