What is your goal hp or good mpg.
You can install ls motor with front mount engine plate which you can make at home if you got the tools. Also make out of card board and get cut at local shop. This can really cut the cost down but go to research to make sure its proper for your application.
If you run efi be sure to buy a complete engine kit. With engine wireing harness and all asseories on the engine and computer attached to the harness.
Now if all you have is a motor and trans i would use a carb setup and make some serious power out of the motor. Since the efi isnt the limiting factor.