Whats your budget?
What do you want in performance?
Do you want an unleaded engine?
Is insurance an issue?
Any conversion will cost you more than you thought, even going for a carby fed 1600-2000 you have to consider exhaust mods, fuel supply, changing throttle linkages etc. Not to mention brake and suspension upgrades that the engineer will require. Then theres part fabrication to get it all in.
There are plenty of great engines in the Toyota stable, you just have to figure out what kind'a performance you want and how much you are willing to spend to get it.
If you are just after a modest increase in performance, the most cost efficient way is the traditional route of cam, carbs and exhaust on a good condition, original type engine.