If you go with a BBC, you can't go wrong. There is a lot of knowledge that is easy to obtain and lots of parts for them.
For the most part, go as large as you can or want to afford, using good parts. There is a saying, "THERE IS NO SUBSTITUTE FOR CUBIC INCHES" for a reason. There are exceptions, but only seldom.
Keep in mind that the guys running the lighter motors are still making them as large as they can, That gets expensive and requires specialized parts.
The LS motor is a good motor for what it is designed to do, but saving 300 lb. in a heavy boat is a small percentage of the over-all weight.
I think the 300 lb. difference may be overstated. It appears for there to be a 300 lb. difference, it would have to be an all aluminum LS compared to a steel BBC.
All aluminum BBC's are available too, but at a price.
Remember, you don't have to use all the power available with larger motors, but if you decide you want more later, it means changing major parts and that is expensive.
The larger the motor, the easier it is on parts too.
If performance has anything to do with changing motors, keep in mind that no cares if it is a 283 motor or a 600 inch motor, if you are slower.
:smile17: