Need answers on an idea I have

[onefast5.0]

Ok,I have been planning my build a little at a time and I have had some thoughts come up,but not sure of the answers.
This is what I come up with,I want to know if I bought a basic kit,do I have to buy a donor car to use everything off of it or can a pick up things as they come along.I am really leaning toward a 302 or 351 carbed motor.
I haven't ever built a motor,but I really want to do something like this on my own with books and help,of course.I want to know my car inside and out and learn alot through the process.
I know I want a manual trans definitely,I also have seen some people on here and the other site use the explorer motor.If I go EFI,I need the ECM and all,I guess.If I go carb,I am assuming that can pick up some things on craigslist,and work on it a little a a time to get my desired results.
As far as rearend,I'm thinking I can find one of those as well from craigslist or my local salvage yard.rack and pinion,Summit Racing perhaps?
I'm not sure that is why I would like some input to make sure I am on the right page.
Any suggestions are greatly at appreciated.