This is one of the most dangerous actions on a lift truck I know several people that have lost fingers , hands , arms and their life doing this
If you are uncertain about this repair get professional help if determined to repair ,chain with a good quality heavy chain then double it for security those are telescopic cyls
Not hard to disconnect but very heavy and bulky you will need another lift or another person to remove safety good luck and be safe
Remember no such thing as too many chains
As far as blocks be sure they are oak or other dense wood if you use them