the approx .8:1 compression increase the ~9cc smaller chambers the mag heads give will increase power by about 3-4% alone on a stock 360 short block over standard LA 360 heads, not considering the better combustion chambers, larger curtain area of the valves, and better flowing ports. comp XE268 wouldn't be a bad cam for a light car with a stock 360 shortblock/mag head combo, if it's a heavier car I'd drop down to an XE262.