Harmonic Balancer Question

I have a 68 340 engine. I am currently assembling the engine after a rebuild and was going to replace the harmonic balancer. I bought a new Pioneer balancer from the machine shop that did the machine work on the engine. When I took it out of the box, I saw the timing mark in relation to the key way was quite a bit different than the original. I thought that maybe the outer ring on the orginal one rotated. I installed it and found that in fact, the original one's mark was accurate and that the new one was the one that was way off on the timing mark. I brought the engine to TDC and marked the new balancer. However, after I did this, I went to install the crank pulley and the bolt holes don't line up. I recall that they changed the water pump in 1970 and I guess that they also changed the timing cover and placed the timing marks on the other side of the timing cover. So, my question is, without changing out my water pump, timing cover, pulleys, radiator, etc., can I get a new balancer for my 1968 engine? If so, and if anyone would have a part number, that would be great. Thanks.