You'll also need a V8 bellhousing for a 55 2nd. series or newer and the corresponding crossmember, and you'll need to convert the truck to an open driveline, which usually involves changing the rear axle or modifying the torque tube rear end to an open style driveshaft. V8 conversions on trucks prior to mid-year 1955 are not quick, simple, or inexpensive, no matter which engine is used.
Jerry
I'm going to tell my son about your post.
To the OP if you are set on the v8 swap I would go with the 283. I had a 67 283/195hp 2 bl carb Impala with power glide and it had plenty of power and good MPG. Unless you own a lot of oil wells I would not go near a 409. Jeffrey
