Any reason swapping an engine from an '87 300td into an '84 300td is a bad idea?

[forjanice]

This may seem like a foolish reaction, but I seem to be having some gasket issues -- white smoke from engine, coolant and oil rather quickly, etc. This is happening in the '84. I also have an '87 engine with half the miles available to me for $500 bucks. It seemed smart enough, possibly easier, and maybe cheaper to just go ahead and do the swap, rather than doing necessary repairs on the existing engine. Am I right about this? Is there any reason an engine swap from an '87 to an '84 may be more complicated than I'm imagining?