Heres the different types of drop tank used on P-47s.
200 gal ferry tank.
Flush fitting, and only used on P-47C's and early D's with the flat keel.
These were used operationally in the ETO by the 4th, 56th and 78th FG in late July and August 1943. Despite a 200gal capacity they usually carried only 100gal as, amongst other problems, they were unpressuried and fuel could not be drawn from them over 10'000ft.
75 gal tank.
Using air pressure from the vacuum pump normally lost in the exhaust, thermostats sourced in the UK, and the glass elbow tube designed to stop the tanks "hanging up", fuel was now able to be drawn at high altitudes and this became standard for the 75 gal and other tanks.
Introduced at the end of August 1943.
108 gal tank.
Introduced later in 1943. 2 types. Pressed paper and metal. Pressed paper, coloured silver, were manufactured in the UK due to a metal shortage. The USA manufactured metal tanks were painted grey.
At the beginning of 1944 the wing pylons started to be fitted, and plumbing for fuel installed. P-47C's didn't have the "wet wings" and were unable to carry fuel tanks on the wings.
150 gal "slipper" tank.
Introduced in Feb 1944.
200 gal flat tank.
A rush design at the end of 1944, intended to allow the wing pylons to removed from the 56th FG P-47s and still allow the maximum amount of fuel to be carried. Slightly wider and flatter than the 150 gal tanks. Often seen under the wings of the P-47M though.
Outside of the ETO, 3 other types of tank were commonly seen.
Im the MTO and PTO for example, the 110 gal tank type more usually associated with Mustangs were used by the 79thFG amongst others.
175 gal "teardrop" tanks,which could only be carried on the wings due to the limited ground clearance under the fusalage.
The "Brisbane Tank".
Manufactured by Ford Motor Company in Brisbane Australia as a temporary measure due to long shipping times from the USA. Essentially a field modification.