The Airstream weights PDF circulating around shows a 2003 25' Safari as 4920 empty 680 hitch 6300 gross & 17.75" hitch-ball height; my copy does not list 2004 models.
I have a 1999 standard cab short bed 5.4L F-150
and my 27' weights are a little lighter than yours - 4570 empty 500 hitch 6300 gross & 19.5" hitch-ball height. I saw 9.5 to 11.5mpg on my last long trip.
Going above #500 hitch tongue weight (TW) usually means upgrading the hitch receiver to Class 4, you're lucky (or smart
) if the existing hitch TW and capacity is greater already - and going with a solid forged ball-mount shank (#800/1000 rated) and a similar rated ball with ball shank at least 2-1/4" long. etc. Keeping the ball-mount pin hole to center of ball hole length to a minimum (some are exaggerated length) will improve handling fractionally but at the same time reduce clearance when approaching a jack-knife angle.
Anyhow; the #630 hitch weight is getting up there enough that weight distribution bars would be appreciated, yes, there is excess payload capacity and all that but that's 630 pounds beyond the bumper and putting some serious leverage on handling characteristics... as in, with my short wheelbase, occasionally there is tail-wagging-the-dog feedback and a want-to-go-straight at highest
highway speeds sensation which is white-knuckle time.
Maybe boost the front tire pressure some to firm up those sidewalls so the side-to-side 'rocking' is quenched.. Have the brake controller adjusted for the road surface you'll be driving over, the 15 miles of shale chips getting to the 'Lake' want a different setting.. Keep the break-away circuit in mind, charged battery and free clearances on the cable.. Never underestimate the prankster lifting the latch lock at a truck-stop, inspect before moving every time
the vehicle goes unattended.
Beyond that there is only a few hundred items of concern, can't say I hit all of them. Mostly it's when in doubt ASK!