I'm trying to help a friend source a good 3FE inline 6 engine or long block for his 1988 Toyota Land Cruiser.

Any leads would be appreciated.

That's a tough one.  I'm betting it would almost be easier to swap to a different engine, than find a 3F-E in good condition.
I'm thinking something like the newer 1FZ-FE would be easier to find.  I don't know all that's involved in the swap, but it's been done.  Plus it's 60 more hp, and 50 more torque in stock form.