Since you happily admit that you will believe bull**** if it sounds like what you want to hear... Sure bud, I have just what you need. Cash app me $1375 and I will send you a can of magic s*** that will gain you 195 HP and 27 MPG. I promise it will work. If it does't I will tell you that you just used it incorrectly and ****- all if you want your money back.
Seriously ?
While you do not come right out and state it, it is pretty clear that you are not coming from a position of high expertise and experience in the subject of Land Cruisers. Not a damn thing wrong with that. Most people are pretty informed and knowledgeable on something. No one is highly informed and knowledgeable on everything. But you might want to listen to the advise that you came here to solicit. Even if it is not what you want to hear.
If there was a magic answer to gain power and economy in your Toyotas... why would we not all be using it?
But ignoring all that, here is a straight up answer to your question. Your '80 does not have a "chip" that can be replaced. IF you wanted to alter the ECU, you would have to replace it completely. Hardware not software. There is no "upgraded" ECU available. There ya go. End of quest.
I guess that you could try the magnets on your fuel line, the tornado generator in your intake or maybe the hydrogen brewery under the hood too. If you could find one of the old Jones Schneider DeKalb units that would certainly do the trick. But it has been years since I even heard mention of those.
Mark...