Magnum flex plate 904 vs 727: identification?

It seems like the magnum flex plate topic is voodoo...

I'm just going to assume that I have a 727 diameter flex plate since they're presumably more common. :(

I just called Performance Automatic just to see if they had the right flex plate and the guy knew nothing about Mopar flex plates...they didn't even sell them (despite offering quite a few choices for Mopar transmissions).

If I'm reading the "Magnum Swap" page correctly, I will have to buy a standard Ram/Dakota Magnum Flexplate, then get a torque converter that is weighted specifically for a Magnum...and there's basically only one shop in the whole world that will make one of these?

:wack:

How will I know if the diameter of the stock flex plate will even work with the 904?

Can anyone generous soul offer any other ideas?

Thanks in advance!!
-Mike
It's not Voodoo. The flexplates are the same for an internally balanced Magnum as they are for an LA motor.

I've got an LA SFI rated flex plate on my 390 that's in front of the 904 in my Dart.