Itinerant Air-Cooled

I have an opportunity to buy, at a good price, both of these engines and a 6 rib transaxle. I have a '78 Westy with the GE engine, and I'd like to have some spare parts, since the pricing is right. What are the differences, if any, between the '78 and '80 engine? Are the heads the same? Hydraulic lifters?

The Vanagon heads are going to be square port, like the 1979 Baywindow has. Hydraulic lifters were how it came from the factory.