Blue,
Check out the motors for yourself. If your heart is dead set on a big block, go for it. For Sunday cruising, you will have no handling problems with them. They will be much faster in a straight line and you can say to everyone who asks that it is a big block.
On the flip side, they cost more. They weigh more, so if you plan to do any racing that involves turns, it will be a liability. They put out more heat, and require more heavy duty (meaning $$) all around. Stronger trans, rear, radiator...
I autox with a friend who has a SPF with a stroked 351W (396 ci). He has 500 hp, and the thing is a rocket. Roscoe's "mild" 351 sure didn't look so mild running around Pocono raceway last summer!
Even my underpowered 302 ran well up to about 100 mph.
Start hanging around Cobras more, try getting some rides. There will be many events coming up. Including the Cobra Revolution a group of us are putting on in Valley Forge Park on June 7th. Come on down and poke your nose around. We'd love to have you. Registration forms will be out in a matter of days.
Steve