360 build.

Jadaharabi said
The 360 flywheel is balanced for 360s only.
68-71. 340 are internal balanced engines and the 72-73 are external balanced.

Its an odd Ball Aussie Borg Warner Flywheel. Its originality a Hemi 6 re-ballanced in Oz to Mopar Spec for the 360. US 360 Flywheels dont fit.

Converted Surface Ground and Balanced Flywheel [Small Block 360]

So yes, it was a bit naughty of me to run it behind the 340 but I knew it was not for long as the 340 was needing pulled and rebuild anyway.