ALL v-8s should have a balance tube.
For one thing, the camshaft timing is designed to take advantage of exhaust scavenging. You can't get that unless both sides are tied together, i.e., balance tube.
Separating the exhausts one side from the other is going to make the idle rougher.
You can hear the rough idle, even on a mild cam, on cars like Cobras and Corvettes with side pipes.
You are giving away torque with that setup. How much? You would need to do an extensive dyno test to find out. I'd take a guess and say in the 30 to 40 lb-ft vicinity.