Before you start trying to realign the headstock, look again at bed twist. No point in using a carpenter's or builder's level, you need a proper machinist's level which is much more sensitive. This topic has been discussed to death over on the model engineer site:

https://www.model-engineer.co.uk/

I suggest you search there, there have been a number of threads on the topic. Ideally the base needs to be at least resting on a level floor if not bolted down, or have levelling screws so it can be sitting on the floor with no distortion. If the base can distort the bed it will. Then use the mounting screws, which may well have a levelling nut arrangement, to adjust the twist out of the bed all the way along. Make final adjustments doing test cuts.

By the way you are not seeing runout, it's taper. Run out is when a shaft is not running concentric.

My Myford Super 7 is mounted on a pressed steel stand which has 4 mounting feet, each one with a screw adjustment for levelling. So I get the top of the stand level using a machinist's level, then adjust the bed mounting bolts to get the top of the bed level transversely at both ends and the middle, turning the level through 180* at each position. Of course it doesn't have to be level as such, just straight, but "level-ness" is a convenient way to do this.