Having just dealt with all of this I can tell you that the B&M 10230 internal balanced flexplate has two different diameter bolt patterns for 5/16" bolts and the smaller diameter for the
7/16" bolts. However the converter I bought has 3/8" bolts so I had to drill the 5/16" smaller diameter pattern on the flexplate up for 3/8" bolts.
I will note that the flexplate came without ever being deburred. I was a real joke for a $150 flexplate. It's all deburred now, but it should have been done before they plated it.
Since my convertor had 3/8" bolts there were no off the shelf ARP option for torque converter bolts. So ended up buying two packages of Chevy bolts and cutting the length down.
Extra money and extra time, but they fit nice now.
Note to the guys that say go to the hardware store and buy Grade 8 bolts have probably never measured the bolt head to back of the oil pan rail, or the cam boss supports on the rear
of the block for clearance. ARP bolts have a .200" thick head on them. With the B&M flexplate bolted to the crankshaft and the ARP convertor bolts bolted to the flexplate there is
.085" clearance from the bolt head to the block/ cam boss supports. Most hardware store bolt heads are at least .300" thick, so this is an area that you need to pay attention to when
assembling your combination of parts, or nasty things can and will happen.
Tom
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