I repaired some frames a few years ago, a 400 D & a 400 E
Although they look very similar at first glance there is actually a few differences in gussets and bits.
Also if I recall correctly one of them has a lower engine mount under the cases and one doesn’t, can’t remember which one is which.
The 400 D 1W4 bare frame weighed in at 11.6 Kg’s
The 400 E 2X4 bare frame weighed in at 10.3 Kg’s