C42 in M38

[cmp truck]

Hi,
I am going through a box that I acquired that contains from first glance, a complete C42 set. I have a number of questions.
The included manual is Operators Handbook, Radio Station C42, Truck Utility 1/4 ton CDN dated 1960. It appears that the set was in a M38. Questions:
are the resilient mounts (rubber blocks) shorter than the J1 box and the 4 Way No. 4?
The mounting NBW (nut, bolt, washer) for the J1 box and the 4 Way No. 4 are 1/2". The manual says 5/16"x11/4".
There are four "washers". They are like a mini coil. What are they for?
The set has a base and a carrier frame as in the manual. Page 8 indicates " position assembled radio set on runners engaging dowels at rear. Secure with two hand clamps at front." These runners and clamps are not present.
A large 27 1/2"x13 1/2" mounting plate did come with the set. It is stamped 5820-21-850-5914.
A spare tire mount for the ATU also came in the box. I am thinking that the set may have been in a M38 at one time, but for some reason changes were made which would account for the large mounting plate.
Photos attached.
Comments welcome.
Ian