Find out what type of gears are in the car,
if you got something like 2.73 gears, dtich them, and get some 3.73's, this will give you more torque off the line, but you'll have to sacrifice a little top speed. you can either buy a new Ring and Pinion set, or u can look for another G-body axle to use that already has the good gears.. After doing that... get a pair of headers with dual exhaust, and then a cam. if your going for low end torque dont get a high duration cam. i believe that lower the duration the more low end power you make, but then you might have to sarcrifice a little top end power, so try and get a cam to even things out. and its a good idea to get a double roller timing chain, just cuz it'll be convenient since the timing cover will already be off during the cam swap. Not familiar with 267 Heads
but you can maybe even try a pair of 305 heads?
i know most of them have 1.84/1.5 valves in them, dont know if they're bigger than the 267 heads. but its worth looking into...