To do the job correctly you need to use calipers that are designed to be rear hung. The later model FMJ cars came with rear hung calipers and a rear mounted hard line so that is the setup that you want to copy.
The front mounted caliper on an A-body is the same part as the rear mounted caliper on an F body. Just the right and left part numbers are switched; that is the part number listed for an A-body right is a F-body left.
When you switch the spindle & caliper side to side to rear hang them you do want to use the F body flexable brake lines so you have the correct length. From a functional standpoint the caliper doesn't know or care if its front, back, top or bottom, it works the same: may be some impact on the action of the suspension but that's a different discussion.
