I believe a SFI certifiied flexplate is only needed at 9.99 & faster. But B&M are good to get because they are the strongest, cover all the variances in converter bolt spacing as well as bolt sizes. The Mopar Performance "solid ear" flexplates are an option as well. But I would never use an OEM style plate for regular race use. I've seen many OEM plates crack around the ear ends. But I've broken a couple of the MOPAR versions as well after many years of heavy use.

Be prepared to spend a good bit to internally balance that stroker crank for mallory metal.

A cheaper shortcut would be to use external balanced 360 specific damper/balancer and flexplate to minimize the use of mallory metal.