Would depend on what the chamber size is on the oval heads, the flat top pistons are killing the compression so a pair of oval port heads with the same cc or larger won't do much for improvement. For what it's worth, I've never build or had built an engine that made poop for power below 2,000 rpm, always aimed for the power to come in at about 2,000 and then the engine starts pulling good. Anything 2,000 or thereabouts is barely a cruise rpm, even with the overdrive transmissions and lazy rear gears of today's cars.....