Help me decide!

Just an FYI, the 340 was a much higher-performance engine than the 360 was, so even though the 360 was bigger, it wasn't faster. Now, that does NOT mean you can't build a fast 360, it just means that from the factory 360's were usually set up to be truck engines.

As far as cams, the 256/262 refers to the advertised duration of the cam. That particular cam is the second mildest in Lunati's Voodoo line of hydraulic flat-tappet cams. That particular cam is a bit better than the stock 340 cam because it has a little more lift but less duration and overlap; this translates to more torque in the lower and mid-ranges, but no loss in top-end power. With a little more extreme build you could go with the 262/268 or maybe even the 268/274 cams, but those would kill a little of the low-end torque you need with a "small" engine like the 318 unless you increased the compression.