Thanks, guys.
Took the engine over to be inspected by the PFA and they are happy to issue it with a logbook as if it were a recon engine and it will be 'on condition' like most PFA engines. Two ADs on the carb to sort out (Venturi and float). Fortunately, this engine is complete with the exception of exhaust manifold and starter.
PZL evidently rated it at 116 hp due to the Polish regulations requiring absolute proof of rated power on a dyno. Interestingly, whilst looking through the internet I found a site for Corvair engines where they ran an O-200 Cont on a dyno and came out with way below 90hp for the engine!! A bit like Cessna fuel gauges, the factory figure shown bears only a vague resemblance to the actual figure.