Updates:
@ Michael I followed your advice and "vectorized" the complex to mag^2 block creating a variable for vector length equal to 1024, which I set as the vector length of this block. I noticed that this changed the color of the output port of the block.
Next, I "vectorized" the custom ED block as well. One question I do have is is there a way to find out the length of the input vector that is passed to the block just to confirm that there are 1024 values being passed? I checked the length of the input_items used in the work function and it prints 1, which I'm assuming is equal to an array of length 1024 since this is the vector length parameter i set in the ED block and also, because this is the vector length I set for the complex to mag^2 block as well.
As a result of making these changes to the custom block, now, I'm simply taking the array of input_items, normalizing them, and then comparing to a threshold as before. I'm assuming this is all that needs to be done assuming the block is taking in vectors of length 1024.
@Marcus I think your question does warrant some consideration and perhaps is the better approach. Besides this approach being easier, and I'm assuming less of a strain on the cpu are there any other reasons for this approach?