Known factory upgrades :

Pz-IIf    > Pz-IVg       > Pz-IVh  > Pz-IVj
Czech38t  > Czech38t(e)  > Pz-IVh  > Pz-IVj
Pz-IIIh   > Pz-IIIj      > Pz-IIIm > Stug-IIIg
Pz-IVe    > Pz-IVg       > Pz-IVh  > Pz-IVj
Tiger     > Koenigstiger
Stug-IIIb > Stug-IIIg
PzJg-Ib   > Marder-III   > Elefant > Nashorn   > Hetzer
Marder-II > Hetzer

Bf-109F      > Bf-109G    > Bf-109K
Fw-190A      > Fw-190D
Bf-110 C/D/E > Bf-110 F/G 
Ju-87B       > Ju-87D     > Fw-190F
Do-17Z       > Do-217     > He-177

T60      > T70     > SU-76
T26/BT-7 > T34 M40 > T34 M43  > T34/85
KV-1 M41 > KV-1E   > KV-1S    > KV-85  > JS-II M  > JS-III 
KV-II    > SU-152  > JSU-152 
JS-I     > JS-II M > JS-III
SU-85    > SU-100
SU-122   > JSU-122

i15    > Hurricane II > Spitfire IX  >>> not possible to change factory back
i16    > Yak-1        > Yak-7b  > Yak-9  > Yak-3 > Yak-9U
Mig-1  > Mig-3        > Yak-7b  > Yak-9  > Yak-3 > Yak-9U
LaGG-3 > LaGG-3 s33   > La-5    > La-5FN > La-7
SU-2   > IL-2         > IL-2/M3 > IL-10
Pe-2   > TU-2
SB-2   > IL-4         > TU-2
