the 3s is a $10k swap, and kinda pointless if your not going for 450+hp, because there's cheaper/lighter engines you can put it to acheive that much
easiest and cheapest is a 4efte, its 135 hp, but can be built to 300 or more, its a tried and true engine with a huge overseas aftermarket
next step up would be a 5efhe, its N/A stock but can take ALOT of boost on stock internals, benefits of this is higher compression, which yields higher figures when boosted
after that you start to spend, as both those engines are bolt-ins, the next step up would be the "a" series engines, such as those found in the infamous corolla's and mr2's
because of the popularity of those corolla's and Levin's, the aftermarket for these engines is HUGE, and the possibiilites are limitless, they can safely yield 450 hp if built correctly, the drawback? it takes alot more work to get these in a Tercel than a 4e/5e, including frame cutting/strengthening, if your looking for a swap to do yourself, and haven't done intensive frame work to a car before, this is not the engine for you
lastly is that 3s....it's big, it's bad, and it costs as much

.....upside? the engine is an ABSOLUTE monster, 700+ hp can be achieved with this setup, and that in a 2000 lb tercel is just untouchable
that should get you started, what it boils down to is how much you wanna spend, and how fast you wanna go
hope that helps