5.9 magnum and the ax15

Is this correct?? I didn’t think a 143 tooth flywheel only fit a big block and that was with a special bell housing or scatter shield.

IIRC the bolt pattern at the back of the block is too tight to get a bigger can on it to fit that flywheel.
Oh, they fit just fine.
The 143t (11") flywheel was used on most all manual small block trucks- from A motors to LAs to Magnums. Only a few V6 Dakotas with the NV2500 used variations on the 10/10.5 flywheel.