How about breaking this out into a bit more coherent set of questions...
1) Did mechanical refrigerator cars exits in the era of this list (pre-1960)
The answer to that one would be yes, so overall, your question is appropriate.
You might then ask
2) What companies had mechanical reefers in our era?
A quick check of the PFE "bible" indicates that FGE (yes, FGE, not PFE) started with 25 experimental cars in 1949 and rostered 175 cars by 1952. PFE and SFRD both added mechanicals in 1952. PFE's first mechanical cars were class R-70-7. In 1955, the earlier
R-70-5 ice cars were rebuilt as mechanicals. Classes R-70-8, R-70-9 and R-70-10 followed on quickly. In 1957 PFE added 40' cars in the classes R-40-29, R-40-30 and R-50-6, all prior to 1960.
Roger Hinman's book on Merchants Despatch indicates that they started producing mechanicals in 1956.
As noted above, both FGE and SFRD also had mechanicals in the period in question.
Thus, it might be appropriate to narrow any further question to the particular company that you are interested in and then ask
3) What models are available? (It might also behoove you to first search the STMFC archives using the specific company name and mechcanical, e.g "FGE mechanical reefer".
Ive got 2 questions on this type of car,would they fit within the steam era guide lines and if not then PLEASE ignore this question and if they do who offers a HO(either kit or RTR)for these cars..?????