RE: What turbine to use for the Yellow A-4 Skyhawk??
If you want a Funsonic in North America you have to go through Robart, who is their exclusive NA distributor. If you look at Robart's website the prices for their small engine are $2350 - 2595 depending on which version you get.
I don't know if Robart is equipped to service them in the USA or not. For my money I'd stick with a known quantity that has a good reputation and presence in the USA.
Joe