I think that the main reason why Toyota wont release the 70 series in the US is safety, or at least that would be their main excuse now a days.
Back in the mids 80s when it came out I think it was up to the minimum safety standards so I believe that the reason why they didn't bother to try and sell them in the US is because they might have thought that they were to basic or "plain", because lets not kid ourselves here, the 70 series is a no nonsense, function over form work vehicle and IMO there really isn't a real market for a rugged workhorse like the 70 series in US industry, the F-150 has been the best selling truck for the past 20 years for a reason, americans like comfort and covnenience in their work trucks.
I still think they could have still released the 2 door short wheelbase versions to compete with the Jeep Wrangler YJ succesfully though.
But oh well, you guys in the US get a bunch of other cool toys, you can't have them all ;p .