Square decking the block would be a good addition to your machine work...the only "weakness" of the 318 is it's lack of compression and the rather small 1.78" intake valves. I used to bowl port them and drop in a 1.88 out of a 360 to help the power....pretty nice power gains for relatively little $$$ effort and often better in heavy cars than opting for the bigger port 360 heads. The respond very well to "old school" hop-up parts though, but at 4000 pounds build for torque, not top end power. The old comp 268 High Energy cam works well with a 9:1 shortblock, a decent dual plane intake (even a stock 340 works pretty well) and a 600 Vac secondary holley 1850.

Oh...Please Keep the A/C....it's a great option to have and it doesn't really drain that much power....you could always put a throttle switch with a relay on it to cut off the compressor clutch at higher RPM anyway.