My engine was GX head 54/86 cam 11:1 comp on oct98 fuel 40mm webers and lightened fly..reve'd to 8000rpm max pwr was 106hp at 7200rpm.
NOW the most Ive heard from a N/A A series was John Taylor's knife crank roller cam and rockers big ports motec and 50mm quad throttles...126hp at wheels.
With turbos the sky is the limit with funds...F1 used to push out 1500KW with 1.5 litre V6's used to last 5 laps for qualifying and that was it.....
300hp is achiveable but as Chris said not as a daily.
With mild work and twins will have alot of fun out of 110rwhp in a car thats 650kg... its not about outright Hp...