vt,
Here's my advice...
A 1994 van with 160K miles tugging 6500#'s could easily let you down from a mechanical failure...however that could be said about a 2005 with 80K on it...one never knows when a mechanical failure is going to surface.
The van IS a proven performer for you.
You have much invested in that Pull-Rite hitch which likely can NOT be moved to your Ex...and a new Pull-Rite will likely set you back close to $2K for a NEW one...plus I'm not sure if you have looked at a Pull-Rite installation option on an Ex...it installs BELOW the factory receiver which reduces ground clearance...the good news is that you likely do not NEED a Pull-Rite for a 27' TT...I towed my previous 27' 7500# TT thru the Rockies, Big Horns and Black Hills with nothing but a Dual Cam hitch from DrawTite and a rear sway bar...the Ex is that good on a TT of your size pretty much in stock form with a good WD and sway control hitch like the DC or Equal-i-zer BRAND hitch...
My experiences in a northern climate tell me that 4wheel drive is a must. Plus I have been in some campgrounds and camping sites that REQUIRED either 4 wheel drive OR having a bowtie or dodge push my TT into the uphill site in wet grass or loose gravel...so I'll keep my 4x4 for those FEW times I NEED it...cause when you do...you DO!
Also like I eluded to above...the Ex with nothing more than a good WD hitch and rear sway bar makes for an awesome TV in pretty much stock trim for trailers of your size...I didn't find a need to add the RAS until I dropped 1100#+ of tongue weight on the rear of the Ex...
An Ex with V10 and 3.73's would be a great match for your TT...however if you have any idea that you will be going heavier on the TT in the future...the 4.30 gearing is a PERFECT match IMO to the V10 for towing heavy...but I also found that for my 7500# TT with 3.73's...I simply locked out OD and she would pull all day long at 63-65 in 3rd without downshifting...
MPG's...you will very likely see very similar mpg's as you currently are with your 5.8L V8...and you may even see higher...mpg's are very driver dependant (along with many other factors)...and if you can achieve those with your current TV...you should have no issues with a motor that doesn't have to work as hard...and considering those 3.55's were not really an ideal towing gear...you may see better towing mpgs...but keep in mind the Ex is one HEAVY TV to start...so your combined weight rolling down the road will be significantly heavier too...so mpg's may be a wash...
I know that I have hauled a TT 18,000 miles in the last 3 summers with my family inside the Ex...everyone is more than happy with the comfort and ROOM afforded by this TV...and I am more than happy with the POWER of the V10 for some pretty serious grades and altitudes in the Rockies as we roll down the road at 17,000#'s combined weight...
The overall towing stability and interior comfort is something that cannot be denied...now just getting over the emotional attachment is another thing.
Towing puts a large strain on vehicles...and it may be time to upgrade just for piece of mind...but also given the area you live...4wheel drive also affords piece of mind when the road conditions worsen...my Ex is primarily my Snow and Tow vehicle...two things she does exceptionally well...I don't ask her to be a fuel efficient commuter box...that isn't something she is built to do...I ask her to do what she does best and she keeps a BSEG on my face...
Let us know if you have any questions...I think we all are kind of biased towards the awesome nature of the Ex...so if you want someone to tell you to keep the van and not get the Ex...you need to post this question in another room!
Seriously...let us know how we can help on any specific questions you have on the Ex you are looking at...post a VIN number here and someone can run an OASIS report for you to tell you how the beginning life of your candidate Ex has been spent under Ford warranty!
Good luck,
Joe.