I've never heard of anyone talking about Forest Ave. (pre-MLK change) ever being a part of a one-way pair before, even though I've seen all but the wider-scan map before. I'm not sure if the Grand-Forest arrangement was used exclusively or just Grand or some time was spent using each arrangement. As far as the connecting street on the NE side, it could have been Ervay. I thought about Harwood at first, but its downtown one-way direction has been south, while Ervay's has been north.
As for Good-Latimer, Central, and Pearl, I think only 1 of those was used at a time, even though all 3 are given equal treatment in the mapping. They've all been somewhat major arterials in downtown at least since the 1950s, whether one of them was signed as US 75, or the other.
It would help tremendously if one of the mappers had a close-enough scale of the downtown area, but wide enough that it went out a little farther than downtown. Unfortunately, Mapsco wasn't around until 1952, which misses much of the early US highway incarnations; the only oil-co that was really close (that I've seen so far) was one of the Esso/Enco/Humble ones, but it wasn't mapped east of Central, nor far enough south to include the Grand-Forest Ave. area.