Stick with the small block as stated above. Also gas milage is much better. Those new small block ford engines produce some amazing horsepower, and if you put in a computer controlled one, you can tune it for what you are using it for! The 351 would be a very cool twist for a coupe, lots of power, and a classic in it's own right!
Some of the guys here have mentioned some problems with the Ford engines related to the length of the engine with the water pump installed, but they have also mentioned solutions. Read Don's (Itoldyouso) recent threads for his 27 build.
Of course you can always use a chevy, which alot of folks chose because of the above mentioned problems, and the cheaper to build reasons. I'm a Ford guy, so I say a good 289, or 302 would be nice!
Whatever you chose have fun!