/6 sitting up for several years what to do

Well I think the slant is toast. I drained the oil out of it today and out came a whole lot of anti freeze the oil, I tried to rotate it by hand and its locked up I cannot even budge it.I have a 67 slant sitting in the garage from my Barracuda so the qestion is do I remove this one and replace it with the 67 engine? What to do