As said above, you have to make sure you own the rights. If you do, then you can try to sell this as a PB but do be up front about it's history. And I don't know if a publisher will look a it since most don't want anything previously published. You simply have nothing to lose but time. (This sort of thing happened often in the heyday or short stories. Many became novels.) The title does not matter. Titles are not part o copyright.
V, I've seen magazine stories turned into PBs by the magazine. Highlights stories pubbed by Boyd's Mills for example. Were the ones you're thinking of put out by separate publishers?