Car chip!!?

[slipknot]

Hi! I'm new on this...

If I got a 305tbi engine, whit edelbrock headers, holley 3210 fuel injection, edelbrock Round Air Cleaner, 3" Exhaust System all the way. And modded Intake from 45mm to 52mm...
And maybe I will install Fireball Hi-6 ignition 6440...

Do I have to map my engine?..

How will I know whitch chip I should use?.. If I buy a chip that it's already progged.

Have seen some chip on e-bay.. don't know if they work?..

And if I map my engine, whitch file are I'm going to use for my engine... when I burn whit Tunerpro?...

Can someone help me...

Sorry for my english... I'm from sweden...

Thank's!! /slip.