From http://craig.backfire.ca/pages/autos/boxchevy/350/harmonic-balancer
Harmonic Balancer
The machine shop cleaned and stripped the paint off of the harmonic balancer. Now that it is clean, it's easy to see the dents from the previous owner of the engine having used a hammer to install it on to the crankshaft. Some engine builders and shadetree mechanics get away with using a hammer and a piece of wood, but using a hammer alone is not smart, to put it lightly.
The balancer had clearly been damaged by someone installing it with a hammer.
Installation
There are a few ways to install a balancer. One such way is to use a hammer, as seen above. Some very old small blocks didn't have a bolt in the front of the crankshaft, meaning that using a hammer is really the only way to get the job done. In this case, some sort of wood or metal block should be used to spread the load when striking the balancer.
Another way to install the balancer is to use a long bolt, and draw it on by tighening the bolt. The crankshaft of a small block Chevy uses a 7/16"-20 thread in the nose of the crankshaft. When using this method, it is very important that a bolt with the right length is used. If too few threads are engaged, the threads can tear out of the crankshaft. I know this to be true, because I've done it myself.
The third and final way is the best way. COMP Cams makes a tool that provides proper thread engagement at all times, and makes installation easy by using two wrenches: one to hold the tool steady, and the other to install the balancer. The tool is not cheap (about $60) but it is worth the price after just a few uses. Many parts stores will rent them out for "free". Another perk to the COMP Cams tool is that it can be used on a few different domestic and import engines.
COMP Cams makes an installation tool for many crank/balancer combos.
Depth
When the balancer is installed, it can be hard to tell when it has fully seated. Often times, it can be felt when it has finally hit the timing gear and stopped, but when using the "bolt method" to install the balancer, there is a risk of stripping the threads.
On the small blocks I've worked with, I've found that using the gap between the backside of the balancer and the timing chain cover is not an accurate way to tell if the balancer has bottomed out properly. Instead, an accurate way to tell is to measure how far the crank nose is from the front face of the balancer. It should be approximately 1 inch. On this 350, it was 0.990". Being less than once inch is a good sign that it's on all the way.
The depth of the crank snout should be around 1 inch.
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