Which flexplate?

I'm just about to install a new conveter I bought from Dynamic and noticed the bolt pattern is different than the existing converter. The old one has a 11 1/8" pattern with 5/16" bolts. The new one is 10" with 7/16" bolts. Is there a stock flexplate that'll work with this aftermarket converter, or do I need to buy an aftermarket flexpate???

Engine is a '68 340 w/ forged crank and I noticed there are 6 bolts holding the flexplate on the crank. Trans is a 727 if that matters.

Thanks guys.