Bitter taste of defeat! So much coolant in the oil pan.

compare coolant passages in head to the ones in block, may need a different head gskt.
And your intake gskts may be wrong if using 4v intake on 2v heads.
Don't be too concerned with getting all the "milkshake" cleaned out. Your first oil change will clean out most of it. Use a cheaper oil for the first one!
Good Luck!