New 4runner owner :)

[89FourRunner]

Manual hubs are a good idea, the vacuum ADD system seems to be a point of failure. Use the stock Aisin hubs, don't waste your time with anything else. Get them at a wrecker or find somebody parting out.

Headers aren't any cheaper for the 3.4, you'll spend thousands on a swap. If I were going to go to the effort of swapping a motor I'd rebuild it just on general principles, but you don't have to - the 5VZE regularly tops 250,000 miles without trouble.

He should have automatic locking hubs on an 89, he would also need to do a spindle nut conversion when switching to manual, I THINK.

That is what's next on my own 89.