As a general rule between 50-150 USD, depending on condition. There are exceptions, but, without more info, no way to tell.
around 1978
A Colt single action army (Pre-War) with the serial # 305068 would have been produced around 1908.
probably around 1977
Around 1885.
go to proofhouse .com and click colt serial numbers,this will tell you the age of your colt.
22 cal. single action colt frontier serial# 34170K was made in 1968
A Colt single action 1860 army with that serial number was made in 1866.
Around 1958
Around 1959.
Around 1958.
Your colt single action army dates to 1881 with the serial number you provided.
about 1876