I'm looking at purchasing a 1966 Barracuda that has the standard 273 and I'm wondering how difficult it would be to put in a 318 or at most a 340. Any help would be great. Thanks.  

This is an easy swap as the 273, 318, 340, and even the 360 are of the same engine type.

The exhaust, engine mounts, and transmission should be a direct bolt-in and you'll certainly like the additional power of the larger engine.

Good luck  

Not as easy as you would think. Ihave a 66 VALIANT, same car. The 273,318,360, do not share the same mount bosses. Mine is an oringal 273 car,it had 318 when I bought it. The mounts were jerry rigged to work. Then I dropped in a 360! and had to modifie the mounts again. As I say, not as easy as you would think!!!!!. Go to Laysons Restoration Parts. They have conversion kits for this swap. Headers,  thats another story.  

Schumacher makes motor mounts for the 360 conversion for this car.