The original Basic D&D gives Fighters a raise of 2 every 3 levels, Clerics a raise of 2 every 4 levels, and Magic Users a raise of 2 every 5 levels.
I'm assuming that Fighters are going to have 1 for 1 progression, which is to say that they will get +1 every level, so I worked from there.
I divided Cleric(2/4) into Fighter(2/3) and got: .75, also known as Three-Quarters, the Cleric progression from 3rd edition?!
I then divided Mage(2/5) into Fighter(2/3) and got: .6, which is shockingly close to Half, their progression in 3rd edition.
Maybe the third edition design team was smarter than a lot of people assumed, haha!
So without further ado, here's the progression for Sweetgrove Characters: