B-26 is an AH v1.00 model, as are the C.205/C.200 and C-47. The A6M5b came later, v1.05 iirc, and the P-40 much later around v1.12. The B-24J is one of the original AH v2.0 models, along with the Ki-84 and T-34/76.
AH 1.xx models remaining to be updated, in alphabetic order:
A6M2
A6M5b
A-20G
Ar234B
B-26B
B6N2
Bf110C-4b
Bf110G-2
Boston Mk III
C.202
C.205
C-47
D3A1
F4F-4
FM2
Hurricane Mk I
Hurricane Mk IIc
Hurricane Mk IId
Ju87D-3
Ju88A-4
Ki-61-I-KAIc
Ki-67
Lancaster Mk III
LVT(A)2
LVT(A)4
M-3
M-8
M-16
Me163A
Mosquito Mk VI
P-40B
P-40E
Panzer IV H
SBD-5
TBM-3
Tempest Mk V
Tiger I
Yak-9T
Yak-9U
Logically, the aircraft which have not been updated that receive the most usage should be the next ones to be updated. In the Late War Arena of Tour 122, the top 10 most used AH 1.xx models are as follows:
Panzer IV H: 68676 kills/83800 deaths
Tiger I: 7407 kills/2021 deaths
A6M5b: 6727 kills/7518 deaths
Bf110G-2: 6383 kills/10177 deaths
Hurricane Mk IIc: 5865 kills/4425 deaths
A-20G: 5045 kills/3140 deaths
Tempest Mk V: 4675 kills/665 deaths
Lancaster Mk III: 4281 kills/18223 deaths
Mosquito Mk VI: 3783 kills/4360 deaths
Yak-9U: 2958 kills/2652 deaths
Those should be the priority for updating.