You can safely run a head with a 4ohm load into a 8 or 16 ohm cab. As long as the cab is equal to or higher than the head's load, it's fine. It won't be quite as efficient as running it with a 4ohm cab, but it'll still sound fine.
Most 4x12s out there are rated over 200w and are 8 or 16 ohms, so would work fine with your amphead.