CLUTCH GRINDING NOISE / BH MISALIGNMENT

Is it possible that say, ...........the bell hole is not entirely "round?" This might lead you astray. I'm assuming you aligned it using a dial on the crank, rotating in the bell hole. Is it possible the pilot is out of center (not concentric) with the crank/ flywheel mount?

Also did you check it for the transmission face being parallel to the rear of the block? This will "tip" the gearbox off one direction or 't other regardless of center.

By the way I DO NOT LIKE scalloped clutch setups. I had "continuous" trouble "back in the day" with my '70 RR 440-6. It would run fine for a few hundred miles, but a few hard shifts would generate "fuzz" on the outside of the disk, which would drag on the pp bolt bosses, and inhibit clean release.

At the time I put the 340 in the car, (same 18 spline 833) I used the factory 340 clutch, and later, changed to a Corvette 10.5 diaphragm in the car. Either clutch INSTANTLY caused cleaner, easier shifts with the gearbox.