Pre Model 18's have an internal firing pin for rimfire 22lrs.
The K32's were centerfire frames like the 38.
I am not a gunsmith but would think it would be easier to convert a K38 by replacing the cylinder and barrel,
I have seen people convert Model 19 barrels to .22lr by turning down a rifle barrel on a lathe then inserting it the 38 bore ,
A .32 insert might be pretty thin to insert in a 38 bore.