91 celica st engine swap

hey i have a 91 celica st with a 4A-FE 1.6L engine. i want to swap the engine for something with a little more power, i want a direct replacment without having to make major modifications to make it fit. i have heard that the 5A-FE 1.5L engine will do just that, but it has less HP than the one i have in it now. which engine would you recommend i put in?