Good point Vince. The ORD 9 can be challenging to obtain info from sometimes. Often times we must play Sherlock Holmes with it.
Note that both the top valve train oil supply line (Tube) and the gauge sender line (Tube) are the same size. Armed with this information re-visit the ORD 9 pages 53 & 54:
Just a wee bit of Sherlock Holmes and Voila there's most of the answer.
When you see a tube assembly broken down into it's individual parts and a spec # appears next to a part you can usually find that spec # in at least one of two places. In this case we found it on the following page further down the list. But you can also find common hardware and bulk items such as this listed in the back of the ORD 7 SNL G-758 and the ORD 8 SNL G-758.
The fact that the original lines were steel comes from the factory drawings.
Anticipating your next questions:
What is the ORD 7 & 8?
They are ORD 7 Organizational Maintenance Allowances (organizational represents the using unit's motor pool) and the ORD 8 Field & Depot Maintenance Allowances Field meaning central motor pools and Depot means Depot. Maintenance Allowances are those parts authorized for use &/or stocking at that particular level in the Army.
What about the fitting dimensions as well as the bulk materials?
They are listed in the 7 & 8 under Group 23 General use standardized parts.

Note group 23!

Note I found one of the two connectors and the elbow here on this page. I did not find the connector 148072 probably because it is a newer number and is probably a supersedure.

Not I did not find 137396 Nut, flared tube here on this page.

Here I did find our tubing under bulk material.
What about the two items I didn't find?
Here's where we learn how easy it can be to find info on Google. You google the available part numbers and spend a little reading time.
For example: I google "137396 nut flare".
One hit is:
http://www.cj3a.info/sibling/m38/tubes.html
Bob Westerman's piece on the CJV35 underwater vent system plumbing.
Shows an application but this 2nd Hit shows alternate part numbers:
http://www.partsources.net/41w3-16-105x ... 37396.html
In the alternate list you find: Eaton (weatherhead) part number: 105X3 4730002889390 INVERTED NUT,TUBE COUPLING EATON-AEROQUIP INC DIV FLUID CON
Now google "105X3 Inverted nut, tube coupling" and you get this awesome list:
https://www.google.com/webhp?sourceid=c ... E+COUPLING