Head is the biggest limit on power. Stock I believe would be lucky to make over 180-200 hp. So depending on your head work you might get to 1hp per cid.
Besides head gearing is /6 biggest weakness and biggest improvement . To take it to extreme example to show the up hill battle of the /6. If you had a 440 (basically double the /6 size) with 2.74 gear and your /6 hp level. You would need twice the gear of 440 to keep up (5.36 ish) not saying to go with that much gear but to me anything under 340 should have at least 3.91 if you want performance. Also could go with 80's tranny for deeper 1st and 2nd not the best solution but at least make light to light more fun.
