There is:
FXT00V (carbureted)
FXT00V DFI (Nikki digital fuel injected, discontinued)
FXT00V EFI (Synerject electronic fuel injected, current)
All three engines are a beast. Although the discontinued DFI model is very temper mental.
All are marketed under the FX1000V name. There is no FX1000E.
The DS22-R:
D is the spec revision. All engines start out with A, then when the spec is revised, be it a part number change, product improvent, emission change, etc., the spec rev's to the next letter. (A,B,C,D, etc.)
The S22 is the actual spec. This designates the OEM the engine is built for, Spartan in this case, and also the bill of materials that go into the engine.
The -R, is the packaging code. The -R represents returnable rack. The engines are shipped to OEM's on a "rack" containing 4 engines. When the engines are consumed, the rack is returned to Kawasaki for more engines. Similar to the rack that the mower itself is shipped on.
When an engine packaging ends in "-S", this means "single pack". One engine in one cardboard box. These are primarily* replacement engines. Replacement engines are bought and sold through authorized Kawasaki Engine dealers.
*some smaller OEM's or lower volume OPE models may use single pack engines, opposed to having their own spec.