Welcome to the sickness, you're in good hands. We understand.

Some of us are pretty biased with regards to our Gen2's. I believe the Gen2 represents Toyota's high-water mark for superiority, quality, reliability, and value. Certainly Toyota still builds quality products, but the era of their late 80's to early 90's cars and trucks were among the very best in class at that time. The quality canyon that used to exist between Toyota and other manufacturers has shrunk to a fine line.
Anyway, to answer your question about engines, the best transplant would be a 3S-GTE. Charlie (a.k.a. white90dx) has a great thread regarding this swap. It's usually found within the first few pages of this forum. Do some searching, and you will likely find answers to most of your questions.
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2011 Regular Cab, 4x4 Auto, N-Fab step bars, Satoshi grille, OEM fog lights, Extang Trifecta cover (list growing, check back often!)