You can get the new ones with a VW engine if you want, I think the SoCal place specializes in that, more old school. Some limitations with that though, that the STI engine or really any modern Subaru would get you past, for instance reliable heat and defrost as well as A/C if you want that (seems like overkill to me). Some use the Sube flat six but I’d worry about it getting tail-heavy.
Remember the Chenoweth dune buggy?