GBVA is right, H&L 8 floorplans are no good to you if you want the firehouse interior to look like GBHQ. What you need is Fire Station #23 plans. These should be obtainable from the LA City Council, since the building is still owned by the city despite being decommissioned over 40 years ago.
Access to the building might also be granted if you contact the Asset Management Division. Just ask nicely

Also, some little tidbits for ya. Peter's office was a set built in the firestation. It is not a permanent fixture, and you might notice its absense in The Mask, Big Trouble In Little China, and when it was in Buffy. Behind Peter's office is a rear door (just like the front door), so fire trucks and ambulances can exit either way.
I've got some info on station 23 which I collected on the net. Have a look, you might find something of interest to you.