Front end question...is it possible?

[HumbleChevyBuddy]

First of all, I swear I tried to search for this topic and I couldn't really find what I was looking for. On to my question, I currently have an '80 Stepside which has the square lights. I personally like the 73-78 round light look. Do I need to change out the entire core support? Or do I just need to get the front grill assembly with the grill I want? Here is what I'm talking about. By the way, mine is NOT the red one...I WISH!