I am currently using vbcc with the os-include headers extracted manually from a quite recent sdk. However, I should have said that the reason I am looking for a compatible SDK is that I want a working gcc and the rest of the development stuff.

The most recent installer directly says it requires 3.5+ and you can only exit, the older ones I have tried starts but fails directly when I proceed. So I just assumed it was for a reason and that it would be simplest to ask for something as old as the OS I am running.

However, I have tried extracting the oldest one I found manually (20110916, claims it needs 2.7) and assigned SDK: to the Development folder. SDK:Startup works fine and most commands which doesn't do anything related to code like awk, make, ssh etc works, but code related like gcc, ld, objdump etc asks for ixemul v50+. So perhaps if one could get hold of an ixemul.library of atleast v50 that works in 1.4.5 it could work.