Penn Central N5k Caboose
One of my early purchases was a lot of 5 PRR cars that I was able to pick up for a good price. It was a great addition to my plans for a PRR / PC based layout. One of the things in that lot included a 36' offset-cupola caboose. At the time, I didn't think much about the caboose, and moved along. As I researched more about PRR railway, I realized I was not seeing any photos of this offset style of caboose. I eventually found out that PRR never had offset cabooses, but I did learn about Penn Central and their N5k model.
In 1970, Penn Central purchased seven offset-cupola cabooses from AT&SF. These 7 cabooses had their cupolas cut down, stove vent moved, a pair of bay windows added, and a few of the windows boarded up. These new, "N5k" series were put in service as transfer cabooses. 
Penn Central put these cars in service, numbering them 18443 to 18449. They survived into the Conrail years, keeping the same numbers.
I have not been able to find photos of any of the 7 ATSF cabooses that were sold to Penn Central, but I have been able to find quite a few that seem to be of the same make. Here is a picture of AT&SF 1567 from 1973 (PC purchased #1564 - so I assume these are from the same line). Here you can see PC 18448 working a yard in 1972, and looking quit clean! Note PC 18448 and 18449 were the only two that had this "peaked" roof. And after 1976, the N5k cabooses were all repainted to Conrail Blue. Here we can see CR 18443 from 1980.
PC 18443 in Youngstown Ohio, 1978. Photo by Al Mixter 
My AT&SF style caboose in PRR colors "out of the box"
My PRR cabin car* is an Atlas model #3583. The "35" series dates back to 1967, and is definitely a "low budget" offering.  Atlas has released a huge number of these models in various road names and numbers. Sometimes they are true to the prototype, and sometimes, like my PRR version, not so true. Ironically, you can get a PC 18443 and PC 18447 from Atlas, but it is in this "35" series mold. So it is the right railroad and numbers, but wrong style of caboose.
The "35" series from Atlas appears to match pretty closely to the ATSF cabooses that were sold to Penn Central in 1970, making this PRR model I had the perfect host to be kitbashed into a PC N5k caboose.
*(The Pennsylvania Railroad called them "cabin cars" instead of "caboose").
First, I cut some thin styrene to be boarded up the windows. I tried to be very careful and only glue from the inside so as not to mess up the outside. I then removed the two roof walks, and cut off the smoke stack. When I cut the stack, I learned that the plastic was black, and the model was painted red. I had incorrectly assumed since the inside was all red, then the plastic was red.
So now I needed to remove the paint. To remove the paint, I covered the body with the paper towel soaked with rubbing alcohol. This got off most of the paint, and then just a little q-tip and brush work to remove the stubborn parts.
Once I had the paint removed, I cut off the copula using a razor saw. I cut it down to size using the tops of the side windows as a guide. This left only the front facing windows in the cupola. Once I glued the cut-down cupola back in place, I boarded up the remaining windows using the same thin styrene.
The roof had these ridges where the walkways had been. I cut these off with a sharp razor. I filled the holes left by the walkway posts and smoke stack with modelling putty and sanded things smooth. I did my best to not sand off the rivets and other details along the roof.
I noticed in the pictures that the ladders to the roof had been removed, but there are these 'support poles' up to the roof. The original model does not have these support poles, but does have a ladder going to the roof. So cut the ladder down to just 1 pole to represent the support. I might add another support in the future.
The Finished Car
I ended up purchasing brass detail parts, and used those for the railing/brake wheel, and I am REALLY glad I did! Here are a few photos of the finished transfer caboose! Next up will be 18443 in Conrail blue! :-D
Assorted N5k Photos:
http://www.rrpicturearchives.net/rsList.aspx?id=PC&cid=1 They don't have any of 18443, but do have a few of his brothers - 18447, 18448, and 18449
https://conrailphotos.thecrhs.org/galleries/n5k-cabooses more photos of the 'brothers' in Conrail blue.
https://rrmuseumpa.andornot.com/permalink/archives189206 Black and White photo of 18446
http://www.rr-fallenflags.org/pc/pc-frt.htm has one of 18443 and 18447
Photos of PC 18443
"facing right" -- http://www.rr-fallenflags.org/pc/pc18443cba.jpg
"facing left" -- http://pc.smellycat.com/pics/equip/pc18443gam.jpg
In Conrail blue (both "facing right" )