B&M Flex plate Question

I have a stock 360 block that I'm bolting to a 904 trans and I'm looking into aftermarket TQ's. From what I understand (please correct me if I'm wrong) all SBM flex plates are the same (unbalanced and the needed balancing is on the converter). B&M has a PN 10239 for this application:

http://www.bmracing.com/products/10...-360-cid/?mk=43&yr=1971&md=2318&smd=&eng=5385

Which from the picture looks to have been balanced, so if this this is the case do I need a balanced convertor? I tried contacting the B&M's tech service line and they seem to be clueless about it :banghead: