Looking at some specs for each not long ago,,I'd leave a J frame 32 alone.

The 32Long max service pressure is something like 15,500psi.
32Mag is only listed in CUP (copper crusher units) at 21,500cup.
There's no formula to convert CUP to PSI.

Some readings in CUP are very close to their PSI reading. Many are not.
The CUP number may be as much as 20% less than it's equivelent PSI.

Proof rounds are 30 to 40% greater than the max service pressure.

Even if the 32Mag CUP is equivelent to PSI (21,500),,the 32Mag would be entering or inside Proof Load pressures for the 32Long original chambering.
Real numbers of what the PSI rating is for the 32Mag could place it higher than the 32Long proof round.

Yes it's probably been done,,lots of things can be done and will function,
But without knowing some hard numbers,,and using a small diameter J frame cylinder of a 30-1,,I'd not do the conversion.

It appears to push the limits IMHO.