27 inches? You lost me on that one. Mine was 53.25" from a T5 to a 12 bolt Chevy from a 1969 pickup. I used DSI...http://www.driveshaftspecialist.com/ Really good guys to work with and they'll give you an Army/Navy/Marine discount if you qualify. An inch to inch and a half of play ought to be good.
The best advice is going to be to have a driveshaft made for you. This way you will get it made the right length, you'll get a new transmission yoke, and you'll get it balanced. There's a world of benefit to a balanced driveshaft and constant misery from an unbalanced one...at any speed over about 40 mph it can be really bad. Here's what I'd suggest about measuring:
1. have the truck completely assembled...bed, bed wood, gate, spare tire, everything.
2. do not have it jacked up...have it sitting on the garage floor or driveway.
3. set your pinion angle. This is important. Read about it if you're uncertain.
4. slide under and measure from the end of the T5 housing (not the seal but the area just outside the seal) to the flat part of the u-joint mount (which coincidentally will be the center line of the u-joint. This is the measurement the driveshaft shop will probably want you to give them.
Good luck.
