Ron,
If you search the P/N 1103841, IM or as we call it DIS box, it is NLA at GM.
Obviously not a great situation if you need to replace it. I also don't know of too many places that even repair our ECM's, let alone a DIS box.
I have a spare IM in my parts stash. I think that a failure of some of an LT5's electronic control "black Boxes" is a greater fear than if you were to spin a rod bearing. That my be hyperbole on my part. It does appear to be easier to replace internal motor parts than to get some of the LT5's black boxes replaced or repaired.
Tom