83 Celica Engine Upgrades

Can anyone help me out with this problem. I recently got a 83 Celica 2 door coupe and have had issues with noises from the engine, mechanics tell me most likely have to get a new engine to save money from fixing problem. What are the best engines to get without having to spend a fortune or what are good 2nd hand engines to look into. What would be a good performance booster. Also are there any good body kits for these cars? or any good modifications to make to get better power.