flexplate question for 360

[busteed]

On my current 360 build (non magnum), I bought a aftermarket flexplatefrom B&M.  It was the externally balanced flexplate for a 727 tranny.  So, my ngine is balanced with this flexplate.  I have changed my mind with the build.  I plan instead on using a 904 tranny instead.  Question?...I plan on buying a different externally balanced flexplate for a 904.  Will I need to rebalance my engine with this 904 flexplate?  Or, is the 904 flexplate balanced the same, with the only difference being the mounting holes? 

[Chryco Psycho]

the 904 uses the same flex plate , But there are 2 bolt patterns for the converter , a smaller &   large pattern , if your converter matches you can use the flex plate you had the engine balanced with

[Highbanked Hauler]

  So the flexplate  with the NOTCH cut in it for a 92 or back 360 does the balancing so there is no need to weld weights to the converter    is this correct

[A383Wing]

  So the flexplate  with the NOTCH cut in it for a 92 or back 360 does the balancing so there is no need to weld weights to the converter    is this correct

correct

[John_Kunkel]

I've been told you can't use the B&M 727 flexplate on a 904 because the outside diameter of the 727 flexplate is larger than the 904 flexplate and it'll interfere with the starter.

Factory flexplates don't have that problem but they're not externally balanced.