Your going to spend a lot of unnecessary money. First of all, being bored .030 over will automatically help raise the compression. So, by the time you do all that work on the 273 heads (bigger valves, hardened seats, porting, milling), why not just use a set of 302's, or even 308's?? The 302's are very easy to get (85-91) 318 and are close chambered heads. The 308's are found on 360's from 88-91. They are not close chamber but have the bigger valves/ports.
My suggestion is this: Because you don't care about performance/high horse power, but all you want is bottom end "stomp" and a good cruiser, I'd forget bigger valves. Just use 318 heads (new enough to already have hardened seats). These are inexpensive. If your not using headers, not racing it, then big valves and porting do you no good. Big valves/ports take AWAY from low end torque. Big cams, valves, ports want high rpm. You said you want low end, so stick to a 318 head and save some money. What you can do for the 318 head is mildly open the intake ports a little to match the intake ports... and this is free because you can do it yourself at home.