Thanks for all of the kind words.
A question did come up recently regarding music replacement that may be worth discussion here. At this time, the pack does not contain music replacement. With that said, a music only pack was created a couple of years ago by someone who goes by PepilloPeV for the Japanese variant of the game. The pack can be found here: https://www.zeldix.net/t2056-nes-gryzor-jap-contra-enhanced-audio-patch
With this in mind, I'm debating if it would be worth it to transfer the graphic work over to the Japanese version (and include an English patch with the bundle as well). But, I'm not sure how widely used the Japanese variant is for the user base. In addition, I haven't even reached out to PepilloPeV yet to see if they would be okay with combining forces. Not to mention, the additional content could be challenging from an artistic workload standpoint. More people may be familiar with the North American release anyway. I'm interested to hear community thoughts on this one.