Quick questions;
Are you running the block plate between the bell and the block?
Are you running a Borg & Beck (3 finger), or a diaphragm pressure plate?
Are you running a magnum motor?
A couple of thoughts;
I just assumed the supplied block plate and clutch ball plate would stiffen the bell assembly enough to use the stock torque arm (Z bar). As my car is a factory 4 speed car, I don't want to abandon the factory clutch linkage for a hydraulic setup.
Perhaps a doubler flange of 3/16" or 1/4" material on the back side of the bell mounting flange, and tying into more mounting bolts beyond the starter pocket would help. Welding flat stock onto the edge of this add on plate turning it into a "T" around the starter pocket would strengthen it yet again. Extending this add on bracket or the supplied clutch ball bracket forward to engine mounting bosses (not unlike the stock slant six bellhousing brace) certainly would work if all else fails, with motor mount bosses, the oil pan rail, or even the exhaust mounting surface of the head all possible tie in points. If you're running a Magnum motor with stock A body motor mounts, tying into the additional pickup motor mount bosses would be a natural. Perhaps just tying the motor mounting flange around the starter pocket to the transmission mounting bolt flange would be enough.
All in all not a deal breaker, just more work.