Because of the additional camber gained in this change you should be able to fit a larger tire afterwards. Stock configuration pushes the top outer edge of wheel/tire outwards where it would rub the fender lip. After Shelby drop it will angle inboard; taking advantage of more room in the fender well.
Don't have to remove the motor. Do a search on "Shelby drop" here for more details....
Your overweight (the car)..hmm.. big block is no match for either small block in my garage. Those big fat Shelby's of 68 were not meant for real performance driving..heck Shelby didn't even build them like my '66. But if you reeeeally WANT holes...I will be happy to butcher up those peerty shock towers of yours!!