[Rev]

You may need to start with basics. Was this a new rebuild or a used 289 that you put in? In either case, start with a compression check. All the cylinders should be within 10% maximum of each other. If the compression is over all low (below 140 or so) then there's something worn. If one is a lot lower than the others then theres something wrong in that cylinder (valves or rings). If the compression checks out well then check the timing. With your car it should be around 10-13 degrees advanced. We know that the carb is good as you have a new one. Does it idle well now? There aren't any vacuum leaks are there?

Even when my car was stock with a 289, a 2bbl., and single exhaust, it still had low end torque and would spin the tires a little when I nailed it. And that was with a 2.80 axle and a C-4.

Your car should have a little more than you describe from what It seems like over the net.

Rev