Hi @rmartin,
yes, you can still access those variables. Actually the new source routine is just a more cleaned up and simpler to use version providing a lot of very useful functionalities that previously the user had to implement by himself. Have a look at the file include/source_library.inc where you can see that this simplified interface uses the original variables while removing some complexity for the user.
If you want then you can also use the “old” source as a starting point. The standard template can be found in the directory src/user/source.f
Cheers
Chris