The height you need depends on how much stuff you strip off the engine: if
you can get everything off of the top of the block, and you can get the
exhaust system off the bottom of the engine, then you don't need much room
at all.

If, on the other hand, you're a mere mortal like the rest of us, just jack
the thing up as far as you can and definitely use an engine hoist of some
sort; it'll make the re-install very, very easy -- I was able to slowly
inch the engine up and down with one hand while steering with the other
hand in order to get the engine mated to the transmission.  I rented the
hoist from Taylor, I think, and it was worth the cash (although in
hindsight I should've just bought one).

I'll pmail you some pictures of my engine pull (admittedly, a waterboxer)
so you get some idea of scale.

Best,
d.
1990 GL -- "Mudskipper"