1965 361 has 265 HP stock 230 ft lbs of torque, 9.0-1 comp ratio, and a 2bbl carb ( just looked it up ), to gain power, I'm not farmilliar with this engine, if it's the same block as the 383 and 440 big blocks, you could bolt on a set of 383 heads, cam, intake, headders and a 4bbl carb and you'd have around 350 hp with the 361, I think the 361 is a rarer engine as the 383 was more popular. Now, if your thinking it would be easier to switch to a 383, answer is, if you want 350 hp at least, could be but, not cheaper, the reason is, as I'm looking at the www.carnut.com specs for the 361-440 through 1969, the 1965 383 2bbl makes 270 horse, the 4bbl version, 315 or another 4bbl version with 330 HP, 1969 383's made up to 335 HP but, in 1969, that year is basicly the best year to get high perf engines because it was when the hp got real bigand those motors are high priced. If you buy a 1965 315HP 383, your still gonna have to put a few parts in it to make 350, which mainly would be a set of good 440 heads, possibly a cam and headders, just about the same amount of work for the 361 but you have the engine arleady, you don't need to buy it.