Nice to see this available again, though the cockpits could use some work and the cars are decidedly overpowered. The early, MkI and MkII, Spits had a 1.1L OHV engine of around 70hp stock, around 80-90hp in racing trim (though over 85 was pushing your luck). Due to emissions and safety regulations later versions, the "1600", were heavier and the engine somewhat choked, so had the engine bored to 1.2 then 1.5L, increasing hp to around 75 (eventually US market cars had less than 70hp due to increasing emissions restrictions); in racing form around 90-95hp, though still the same block/crank so care was needed.
This mod represents both early and late model Spits, but gives all 140-145hp. Performance is astounding, but not realistic (I sincerely doubt any Spit engine could even do 100hp reliably ...not counting the one-off GT6 with a 170hp 2L 6cyl).
(FWIW, I often raced MkIIs and MkIIIs back in the '70's.)