WGDE
Gradius Rebirth
Infinite Lives [g6flavor]
040751D0 60000000
Unlimited use of Konami Code
040708C8 60000000 [g6flavor]
After getting a Force Field, you get
Infinite Force Field for Ship Type A,C, and D
040253BC 60000000 [g6flavor]
Infinite Force Field (Invincible) for Ship Type B
04025DEC 60000000 [g6flavor]
EDIT: I replaced my original code with the updates g6flavor has posted in the responses below making it easier to follow. All credit for these new codes go to him!
Since the code address sometime changes, I remake the code
Infinite Lives
040751D0 60000000
Unlimited use of Konami Code
040708C8 60000000
Thanks for the update. I hadn't seen the lives change, but good to know if it does, you covered it. I have to look through my notes as I was able to find the colelction for power ups, so was always able to force a value, but hadn't been able to much else with it (i.e. set it so you were always fully powered up, etc). I know one of the ships has a good shield where you can take hits from all directions, which through a forced power up you could keep activating it, but wasn't able to find where it was stored (to at least make an invicibility code for that one ship). I'll see if I can find the address from my notes, otherwise was easy to find - search for 0, pick up 1 and search for one, etc. The game is pretty tough and would love to find or help make an invincible code. If you find anything else or want to try to work on it together let met know.
Finally, had some more time to spent on this game. Updated the above codes and these:
After getting a Force Field, you get
Infinite Force Field for Ship Type A,C, and D
040253BC 60000000
Infinite Force Field (Invincible) for Ship Type B and E
04025DEC 60000000
Nice Work! I need to see if I have E unlocked (don't think so) to test your codes. I updated (replaced) my original codes with the ones you created and a note that they are your codes giving you credit for them. I just wanted to make it easier for people to follow the codes but at the same time make sure people know they were yours!