Hi Robert – you are correct that C37 is .008 uF and C38 is .05 uF. As Alistair pointed out, these two (2) capacitors are in the same cardboard tube. Two wires come out of the tube and there is a metal band circling the tube. One wire comes from one end of the .008 uF capacitor, and the other wire from one end of the .05 uF cap. The other ends of theses two capacitors are connected together and connected to the metal band.
To replace this dual cap you can use two individual modern poly caps, .01 uF (instead of .008 uF) and .05 uF. Connect the replacement .01 uF cap between the two lugs on the terminal strip that previously held one wire from the dual cap (the .008 uF section) and, on the other lug, the connection to the metal band.
The lug that was connected to the metal band also connects to pin 2 of the 2A5 (plate) and the output transformer.
The lug previously holding the .008 uF wire from the dual cap should also connect to pin 3 of the 2A5 (the screen grid) and the tone control.
For the .05 uF cap, (C38) connect one lead from the new replacement cap to the tone control, via the terminal strip (your yellow circle), and the other lead to the lug on the terminal strip that used to hold the metal band (but now also anchors one side of the new .01 uF cap). The other wire from the tone control returns to pin 3 of the 2A5 as before.
Replacing the other dual cap C19/C20 is easier. Again, the metal band is a shared connection for one end of each of the two caps inside the cardboard tube, and each of the wires emerging from the tube connects to the other end of each of the caps. Simply replace this dual cap with two individual 0.1 uF modern poly capacitors as shown in the schematic. One end of each of these caps is soldered to the chassis. (I had to search for these two caps on the schematic because they are drawn in very different places!)
For reference I have attached a couple photos of the construction of a dual cap.
Gary in Victoria