My 2001 V-10 gasser, like most, has a 5000 pound towing limit. Combine that with the vehicles that CAN be towed 4-down, you've got some research to do.
Most of it, on this forum, has already been done. Reseach the topic.
I tow a 2007 ChevyHHR automatic. Pull a 2 amp fuse,leave the key in the ignition (to keep the steering wheel free), put 'er in "N" and off y'go.
Also tow a 2011 Ford Ranger 4WD auto. Proceedure is a bit more complicated (and expensive)...you would need a $400 "Transfer Case Neutral Kit"...a Ford only item....and my original towed car was a 1996 Ford Contour, 5 spd stick.
Quite a few other vehicles to choose from, GM seems to have the most in various price ranges, so go for it. Then you need a baseplate for the car/truck you choose...and a towbar with wiring for either the magnetic lights or the diode kits. Thata's about 800+ bucks. See www.blueox.com
That's the outfit I use....I have both vehicles using the same style baseplates, so I can use the same towbar for either one.
As far as mpg....figure a V-10 = 7.5 at best.
As far as the REMCO driveshaft disconnect, I've spoken to maybe 4 owners, and they like the product...but you DO have to keep it "clean" by spraying it quite often with WD-40 or silicone...but they say they're happy with it. As far as the "lube pump"...y'gotta drill a few holes...and to me, that means the possibility of oil leaks...and the price (installed) seems to me, to be too much to be practical....but then again, posters here who claim to have that product are happy with it.
So..whatever you do...g'luck.