I disagree.DO NOT for ANY REASON open up a perfectly fine operating 1FZ to do a pre-emptive HG swap. That's the worst idea ever. Stop listening to the peanut gallery who wants to use your money for you.
I pulled the head off my LX450 after two to three weeks of purchasing. Lots of these vehicles are long in the tooth and in need of serious maintenance. I'd wager at least 60% of the 80 series vehicles on the road need all new coolant and vacuum hoses at a bare minimum. You might as well rip the thing apart, inspect it, and then re-assemble it.
At this point if you're buying an 80 and actually want to take it anywhere I suggest most owners pull it apart. It's also a good time to drain the engine block, replace the radiator/water pump/thermostat/etc. and drain/flush the heater cores.
Most people do a real s***ty job of maintaining their vehicles and if you actually need to service the vehicle on the trail or the side of the road you're pretty much SOL with all that old stuff.
OP - I think you're good especially if you have the paperwork.