Dart heater box interchange

That shows the later, I am looking to see if the later will fit into the earlier darts. Thanks for the link though. The box I'm looking at is non-A/C. Mine is also non A/C. Looking at it, it looks basically the same. I do see about different size heater tubes but that's a non-issue for me. I can easily deal with either changing heater hoses or the heater core itself.