dyno sim 5 is generally reasonably accurate,the factors in bold are mandatory,knowing the other specs helps in more advanced software
you would need the number of cylinders, head flow numbers, ,taken at a standard vacuum reading at every .100 lift stage,
the port cross sectional area at the most restrictive area, the bore size, valve sizes, intake plenum vacuum,
piston bore and stroke , your compression ratio, fuel/air ratio,and ideally, exhaust scavenging efficiency and back pressure,
connecting rod length to do a reasonably accurate ,soft ware dyno
yes you could plug what you know and assume the rest to be similar to some more common engine specs,
but the less verified data, the less accurate the predicted result will be.