Well at the minimum 340 of us took a malaria drug prior and probably after visiting Guadalcanal without any issues. I wouldn't have any problem taking the drug as long as my doctor said go for it.
You were, I presume, a young healthy dude under supervision.
You may, possibly, find that things are different now. Being the old curmudgeon you are now, you'd do well to get a lot better informed than you were back in the Marines(or whatever) 100 years ago.
You may find out that the drug wasn't as safe as you were lead to believe.
I'm not saying that I know anything important about the treatment, I know virtually nothing. I'm just recommending becoming well informed before becoming part of a government testing program, regardless of what your doctor says.
Remember the Tuskegee Airmen?
Tom