This is the Traxxas TRX 3.3 Multi Shaft Racing Engine with Pull Starter. This version includes threaded crankshaft inserts for "short" and "standard" applications.
Now Saito is offering a new engine that offers even more power than the .91 but that's similar in size and weight.
Same mounting dimensions as the O.S. Max FS-70 Surpass Ideal fit for 60 size planes