Using the rocker towers from another head is a bad idea I think. As far as I know rocker towers are bored and milled on the head so they're pretty much matched with it and won't necessarily match up properly on another head.
Also, holding the chain tensioner's position with a screw driver jammed in it is pretty risky as well. If it slips even a notch tighter the result could easily be a busted chain with lots of damage. It's pretty easy to take out, reset and reinstall. No reason to take such risks.

If it ran for more than a few minutes without breaking, you might have gotten away with it. As far as the swapped towers from another head.... you'll find out if that worked out a little later.

If I'm wrong about that and someone reading knows better, please comment.