While the ebay examples are tempting you have to remember that those prices are for original low mileage trucks that have withstood the test of time w/o aging, not restored ones. The rarity of being in like new condition with low mileage is what makes it desirable to collectors. Outside the collectible speculator willing to gamble on future values I think you are about 5-7yrs to late. Neither the current economy nor the economy going forward is going to support a price point of $6-8k for a 30yr old restored stock truck, not when you can buy clean trail ready DD's or 1st gen Tacoma's for the same price or less. I know people keep hoping the economy will turn around, but it is highly likely we are already in the economy of the future right now. We have been in a global economy since the late '80's early '90's, it is just now that we as a nation are having to accept wages that are globally competitive, the "home equity credit card" was our last ditch effort of trying to maintain living standards that are no longer viable in a global economy.
You could restore them and put them away for 20-30yrs in the hopes of there being a collectors market, but that is about as risky a proposition as playing "Russian Rullette" with 5 of 6 chambers loaded. What made the '60's muscle cars so collectible/profitable to restore(not so much anymore) is basic Supply/Demand economics. The number of "Boomers" who in their 50's and 60's and wanted something from their youth along with the money(either actual or credit) far exceeded the supply of cars, which is why rusted out '69 Camero shells once sold for $25k at auction and now you can pick up bolt off resto/mods that cost $250k for less than $25-50k. The collectible market for Toyota trucks will most likely be just the opposite. Given the build quality and the number of units sold, there are far more trucks available now and will likely still be 20yrs from now, so the supply will always be more than demand, especially with the very high probability of "X gens" having far less disposable income as compared to their "Boomer" counter parts. Also unlike their "Muscle Car" counterparts, Toyota trucks didn't have any roles in the movies that would have made people want to go out and buy one then or want one now for nastalgia purposes, like the movie "Bullet" did for Mustangs. The only movies that come to mind are "Back to the Future" and the brief moments of the black 2nd gen, and there was a 1st gen with off road lights in "Tango and Cash"(hitman after Cash drove one in the parking garage chase). In all liklihood we have already seen their popularity come and go during the hieght of the wheeling hobby where non running ones were bringing $2000-2500.
If you are looking for a hobby that can make you extra cash(if you don't count your labor), learn some new skills, and your local market will support it, I would say go for it if. I have been doing this for the last 8yrs or so w/84-up 2/4wd rigs, and have made pretty good extra money for my effort. Granted I am making about half the profit I was 5yrs ago, but I am still making more than the top KBB values. I do get the "It isn't worth that much" or " I can buy one in _____ for less" comment from “tire kickers”, but I have never had to wait more than a couple of weeks to a month to sell one. When I listed this '84 2wd for $2950 about 2yrs ago I thought I was going to have to wait a while, but it sold at my asking price within 12hrs of listing it, I probably could have sold it for more.
It was a full restoration from engine rebuild through paint and interior, as well as swapping 4x4 fenders/bed and sourcing good like new bumpers, interior items, etc. It was also the lowest profit margin rig I have done, I only made a few hundred over costs. It was originally intended for my nephew's first car, so I replaced a lot of components I wouldn't normally have done if I was selling it to the general public.
I hear you on wanting to keep each one you restore. When I started out it was kind of hard to let the first ones go since I never got to enjoy the reward of my hard work. However being able to try out new ideas w/o having my personal rig down and a nice stack of cash when its sold seems to be a fair trade off.