...I appreciate all of the feedback from Bob and others and will correct things both here and on Shapeways. I will try to interpret Bob's info as best I can, and hopefully I will not screw that up.
The point is here that trucks that were not readily available, now are.
Haha...yeah, this subject is of intense interest to me, so I have a tendency to provide more info than is absolutely necessary!
To cut to the bone in reference to your "friction-bearing, outside-swing-hanger" trucks and their use on CCS/IMR CA-3/CA-4 cabooses, here's what's pertinent as to dates:
(1) 1952 would be the earliest your "friction-bearing, outside-swing-hanger" trucks were used, on 50 CA-3/CA-4 cabooses as early as February of that year according to railroad drawings dates
(2) Beginning in 1956 and ending in 1958, an additional 90 CA-3/CA-4 class cabooses were equipped with "friction-bearing, outside-swing-hangar" trucks
(3) In 1975, two CA-3's (25012 & 25049) were modified for pool service, so your "roller-bearing, external generator, outside-swing-hangar" trucks would be appropriate for these two CA-3's
(4) in 1975, seven CA-4's (25112, 25125, 25133, 25176, 26181, 26190, and 25193) were modified for pool service, mandating the use of the same truck, bearing, and generator option
All pool service cabooses were lettered with a large, red "P" on all four cupola sides and is the main spotting feature.
All CA-3/CA-4 cabooses before 1952 would be running with wood-beamed "Q" trucks under them, which are available from Panamint Models (Eric Cox) at Shapeways
Of the 200 CA-3/CA-4's (minus two that were wrecked and scrapped) a total of 147 were wearing the "friction-bearing, outside-swing-hanger" trucks by the end of 1958
The remaining 50 CA-3/CA-4's were equipped with "inside-swing-hanger" trucks in 1955
This means that by 1958, the wood-beamed "Q" trucks had been removed from ALL CA-3/CA-4's and placed on many remaining CA and CA-1 wooden cabooses
Since nobody is mass-producing models of any other U.P. steel caboose class, I won't get into specifics about their trucks
Hopefully, this simplifies the information about when and on what to use these truck models.
Cheerio!
Bob Gilmore