I'm writing my own Marvel continuity and was wondering about people's ages and place in time

What I mean is I'm planning for my marvel stories to take place in the 20th century and wanted to ask the more experienced fans about how old a character is and when they should be alive.

Tony Stark's dad was retconned to have helped in the war in the 90s so when did he have Tony? In my continuity I was thinking Tony was born in the 50s making him to be in his early thirties (which is how old he is when he becomes Iron Man, so I've been told)in the 80s making him present for the Soviet-Afghan war or Cold War.

Are the rest of the Avengers (sans Thor and Steve, obviously) supposed to be around the same age? I was thinking Jan of making only 3 years younger than Hank, what to you think?

Then there's Peter Parker. I've been told he's the same age as Johnny Storm, but there's no way Reed would let a sixteen-year-old on a space mission so I'm making Peter have been Spider-Man for nine years by the time the FF get their powers. That also makes me think of his "amazing friends" Iceman and Firestar; are they the same age?

That brings me to the X-Men. How old are Scott, Jean, Hank, Angel, Gambit, Rogue, Mystique, etc supposed to be? I know Magneto and Charles are supposed to be born around the 1930s, putting them around 50 years old by the time I have the events of my story happen.