5.7/727 convertor ??

You may, you may not, there seems to be enough manufacturing variances that some people can get away without the shim while others need it.

I would assemble the engine and transmission outside the car and see how they slide together. What happens is that as you snug up the bell-housing you push the converter up against the seal, possibly damaging the seal, converter, and the input shaft.

Regards,

Joe Dokes