For the CH250 it seems unlikely that something with an IO-360 is going to squeeze in. The kit spec says max weight of 1450 which is too heavy.
For E-AB the builder can put anything he wants down for gross weight, and quite a few homebuilts have a builder specified 1320 gross even though the kit maker says more is OK, which makes it LSA compliant if it also meets the speed limits. The speeds are harder to check or enforce, but it has to pass the giggle test, and an IO-360 might make the FAA inspector laugh out loud during a ramp check...