I've done extensive research on the disposition of the New Haven Railroad's diesel and electric locomotive fleet in Penn Central and this material is presently being serialized in the Penn Central Railroad Historical Society's "Penn Central Post" magazine. I was actually going to write a book on the Penn Central takeover of the New Haven Railroad but lost interest. I may yet do this, but not anytime soon.
I handed the chapter that I had completed on the NH's locomotives over to the PCRRHS and they broke it up and have been running it in installments in the Penn Central Post magazine for the past several years. They have enough of this material to keep it going for many years to come (each ex-NHRR locomotive type, i.e., GP-9s, FL-9s, E-33s, SW-1200s, S-1s, RS-3s, etc., is being covered in a separate issue of the magazine).
At least one ex-NH E-33 recived the large Penn Central numbers on its cab while in New Haven colors and lettering. I have a photo of this unit and it may have been the only one to get this renumbering treatment. It may not have actually been operated by PC this way and the numbers may have been applied while it was sitting in storage and awaiting overhaul and repainting. The photo was taken at the electric shop in Wilmington, Delaware I think. I have no evidence that any of the E-33s had a PC logo applied before they were repainted black.
The reason that the E-33s were repainted so quickly is that Penn Central abolished electric powered freight service over the New Haven Region almost immediately after the PC takeover. Off the top of my head I can't tell you the date the last electric powered freight train ran over the New Haven Region (I have this date elsewhere) but do know that it happened within a few days of the merger.
The complete details of what happened to the E-33s will be published in the Penn Central Post at some point in the near future, but basically what happened is that the E-33s were stored for a short time at Cedar Hill and Lamberton Street in New Haven, Connecticut (I have the exact timeframes in my manuscript) and were then towed to Wilmington where they were immediately overhauled and repainted for use on the ex-PRR electric freight lines.