Welcome to the forum!
I have a 74 dart with a vinyl top myself.
1. i do have some vinyl top trim, but not all of it...guys part cars on here all the time, just keep an eye open.
2. again look for guys parting cars (4 doors fit also and are constantly parted)
3. i go have a 74 grille with a small crack that i took off of mine
4.i dont think rally wheels carried into 74...fyi.
5. i do have a front bumper, but i'm in OH.
6. probably cheaper to get a dash cover...
http://www.stockinteriors.com/DashCaps.asp?Itemid=11142&MakeId=7&ModelId=136
7.yes, same trans xmember
8.most of the accessory drive pieces are interchangable, and guys throw on an alternator bracket and call it a day...
http://paceperformance.com/i-610589...-products-alternator-bracket-chrome-9456.html
hope that gives you some direction! and let me know if you desperately need a bumper from OH..lol