Stop. Take a breath. Now stop "changing parts" trying to fix an electrical problem. <jo
Now if you do not have a Volt-Ohm meter (VOM) or a test light your next step is to get one. They are not expensive and could easily be purchased from the money saved by not replacing parts that are likely good. Even better is to have both in your tool box. If the $$'s are real tight and you have to choose only one, then choose a test light if you mainly work on cars.
Today's cars have tons of "always on" circuits. Which means they are powered even if the ignition key is off. Did you disconnect the battery negative when doing the work? If not, then likely fuses have been blown.
Note, no where in this reply are you going to be asked to replace anything without
confirming it first. Why? Because to correctly trouble shoot this issue we need to know the status of the parts as this gives us important information. You will be asked to confirm power in and out of specific fuses. Not just "check" the fuse. The best way to do this is with a test light. Put the lead of the test light on a known good ground. Always confirm that the test light works before performing any tests. There is a small piece of metal that is accessible out the top of the fuse. This gives an easy way to "probe" the fuse to check for power. A good fuse will light the test light on BOTH sides. In that way power has been confirmed in and out of the fuse.
The shift interlock depends upon fuses F2.17 and F2.35. Test for power in/out of fuse F2.17. Next test for power in fuse F2.35 with the brake pedal pressed. The ignition key doesn't need to be on for these tests as these are always on circuits.
If no power into fuse F2.35, then there's a fault in the brake light circuit and more trouble shooting is needed.
If you are into testing fuses, not a bad idea to also post the status of fuses F2.33, F2.41, F2.18, and F2.13. It's not clear to me exactly what works and doesn't work after replacing parts. Nor is it clear to me if the fuses replaced were blown and if they blew again after being replaced. Again it's vital to know the correct ID of any blown fuse.
F1=BJB=Battery Junction Box=engine bay.
F2=CJB=Central Junction Box=driver's kick panel
1999-2004 MY fuse panel schedule:
http://www.allfordmustangs.com/foru...r-swap-wont-fire-please-help.html#post2669271