I wouldn't use these as a formula to imitate, unless you want the drivability of a race car, back in the day 1 hp per cid was a fairly radical engine now days you can do it fairly mild, heads is the biggest factor in doing this, heads that make good power with mild cams is gonna be more streetable than the other way around. Next main problem is rpm and gearing needed to make decent power numbers, depending on your goal 0.9:1-1.2:1 hp per cid is a reasonable range, thats peak power in the 4700-6300 rpm range give or take. I'd would look into running magnum heads or at least LA 360 heads on a 273. 318 can run pretty much anything.
