I have a 94 chevy with a 6.5 Turbo Diesel with 213,000 miles.  So far it runs like a champ and always starts.  If the engine ever goes bad I would like to put in a late-model 454.  How hard would this swap be with wiring, etc.  

If you are going to make a swap like that find a complete wrecked or worn out doner truck.  You will need wiring harnesses(with computers), feul system pieces(if you want stock type feul injection), Your 6.5 probably has hydraboost braking that you will want to keep. Are you in an area with emission testing?  Don't get me wrong I like my 454.  But I would think about a new 6.5, or another truck.  If your heart is set on it anything can be done.  

yeah i agree with the other post i would just ditch the truck or get the right motor.

if you ever wanted to wheel it diesel is the way to go if you allready have it.