I've never been a big Pep fan, don't much like his style. I think he would give Morales fits, however, and I saw a lot of Morales from the start of his career. The thing about Pep losing to Saddler, Saddler man-handled Pep, made him mad and got him out of his fight plan. He made him fight stupid. In the one fight where pep kept his cool, he gave Saddler a boxing lesson. Morales isn't going to fight him that way as it is not in his nature.
I don't think Mayweather ever fought at 126 and, if he did, it wasn't same day weigh in. When Pep fought at 130 and 135 his was miles away from his best. I don't think an old Pep would beat a guy as good as Mayweather that also happened to be a welterweight. All things being equal, size-wise, it would come down to whether or not Pep could make Floyd come to him. If he could, he'd win. If not the fight would be so bad nobody would care.