Internal balanced..what damper do I need

what tranny? All 360's had weights on their convertors. neutral is neutral, any 273-318 LA or forged 340 balancer will be neutral. When you say it was a SCAT internal rotation assy, do you mean that its made to get balanced without a weighted convertor or was it balanced for the piston.rod combo you bought with it (and it was balanced TO it)? Internal usually means its got the meat on the throws to compensate for the heavier 360 rods you may use, NOT that its balanced already. You can make any crank an internal as long as you can make the reciprocating as light as the throws.