engine conversion

Has anyone ever converted a carbourated engine into a fuel-injected engine?If so,what would be more costly,buying a diffrent engine and running the risk of your current tranny not being compatible or converting your existing engine?I have a limited budget,as me and my wife have had twins recently,awhile back i bought a 1970 Ford Maverick that needed little work,the only problem i have is the severe lack of power from the motor(it has a re-built carbourated V-6)i have owened 4-cylinders with more power than this engine,it doesn't start in cold weather,i was told a 302 would be a good engine in this car,but,i was also told if i bought a diffrent engine my trannsmission might not be compatible and i would have to buy one.What should i do?I love the sound of a bigger engine but i like the performance of todays engines and i hate to get rid of a newly re-built engine.Does anyone have any ideas or suggestions?Or any ideas on what something like this would cost?Your ideas are greatly appreciated,thank-you. :confused: