These posts have come up before . Google 200 RWHP Hybridz and read so,e of those threads . 200 hp is much more realistic and if you haven’t driven a Z with 200 you don’t have the objectivity to ask for 300. 200 would be a hand full for a street motor. People that have ridden in my 155 rwhp car swear it’s much more. Gearing will help with the fun factor .
The advice above is realistic. These engines aren’t cheap to get that HP goals . Cams, cam gears, harmonic balancers , pistons , valves , port work, hardware, engine control( ignition and fuel) , triples or EFI , $$$$$$$$$$$$$$$$