If they are the correct length, if you do them from the ball-joint side you will need a crowbar or maybe a compressor.
If you do them from the bushing side they should go in without it. Bushing side is service manual procedure on the Firebird.

The tightening of the bushings while the weight is on the car is to keep them from making noise and getting torn up while you drive. The bushings are not meant to move, only stretch. It's not a ledgend, it's textbook procedure. It might make it sit too high too, but only until the bushings rip.