From what I know, FRA-KIX has been 744 for quite a long time now whereas FRA-HND is operated on a 748. At least the last few times I checked.
This is also the reason I usually go for FRA-HND instead of KIX when I non-rev on one of the LH flights. I can then easily hop on one of the NH flights to ITM which operate on an hourly basis with a widebody.