[GMCPaul]

It can be done on the Blazer and before the Blazer cargo floor became available it used to be the only option. But honestly it's easier to remove cargo floor and do the work, you need to reuse your rear Blazer bed support it's very different from the truck though some have reworked truck rear bed supports to work. It's really rather basic to do as it just needs cut to proper length and then bed rear support moved over to new floor and modify truck intermediate bed supports as needed or swap over intermediate supports from original Blazer floor.
If you remove all bed floor mounts and remove bed side bolts then cut welds at rear support the bed sides can be spread out and raised and the floor can be removed. It is easier over all and faster doing it this way in my opinion.
Paul Sr @ GMCPauls