i don't know if this will help, but i have one in my 57 buick, it has three mounting holes like the original one. it's not a direct swap. had to do some cutting on the column and replace the rag joint.
The 605 steering box conversion is notorious for leaking. I had one in my '58 Biscayne. I upgraded to a CPP 500 series box. Much nicer handling, & doesn't leak.