installing engine trans and k with headers attached from the bottom

You are not crazy, it's been done but not by me. Saw a build thread on here somewhere, where a guy installed a Gen II Hemi from below, just as you described. I believe he did it with the exhaust manifolds installed.

Keep in mind that installing the engine from the bottom was the way the factory did it, and still does it.

Unfortunately I don't have any first hand knowledge to walk you through, but at least you'll get a bump.

Regards,

Joe Dokes