The balancer seats against the crank gear, there's nothing else to stop it going forward. the key is obviously damaged from wiggle when the bolt came loose and I have to pull it apart and install a new key as the WHOLE balancer moves back and forth, with the bolt and washer not installed, the described amount. Thats as clear as I can make it.
TA sells the Woodruff key for the crank if you can not find it locally. I find it impossible to torque that bolt by myself, so I just hit it with the impact for a few seconds and it seems to do the trick. Never replaced the crank key, but it seems pretty easy. If you need a balancer, Ebay has them all the time, as does the "Part for Sale" on the board. You could also send it the "Damper Dudes" in California for a rebuild (checked, realigned and new rubber put in). I have had a few done there and I have sent one on a Monday and have had it back on Friday. Cost (if I can remember), is about $120? Way cheaper than a new one. They also sell outright rebuilt ones. http://www.taperformance.com/proddetail.asp?prod=TA_1116A
Make sure it doesn't move... My original 69 350 crank is ruined because after about 150k miles things got loose and it got the vibes. When I went to fix it 10yrs ago, the key was broken and the end of the crank also broken. I was pretty disappointed...
No need for red Loctie as it will be a full on Bitch to get apart due to the fine threads if both threaded areas are clean! If the Balancer bolt threads in with too much play then use Blue loctie!