Just yeserday I seen a ssr racing a firebird with an LS1. From my car I could only see that he had custom exhaust.
for a heavy pickup it sure handled the job well. Even though it didn't win it was close

Those have the LS2 6.9L engine and have a better power to weight ratio than the LS1 Firebird.

The old ones were 5.3s and the new ones are 6.0s