[blau911]

The car, motor and trans you have right now will make for a very nice and quick 911 conversion. Stick with what you have already and make it work. Your 912 is no longer matching numbers and the car has already come under the welding torch (new floors). So the car will not be worth what you will need to come anywhere close to buying a stock 911 66-73 coupe.
On the other hand, a stock rebuilt 2.2E motor with carbs and a 901 5 speed gear box in a 68 912, is the same as driving a 6 911S but with more torque, although slightly less hp above 7k rev's. The car will give you all the joy you will ever want in an early 911.
Work smart, and spend the extra money on the engine and tranny if necessary and re-spray the car rattle can black if you need to spend all the budget on the mechanicals. Drive the car for a few years before getting the money together to have it painted whatever color you want.
Don't doubt yourself now. You have already put the plan in motion by accumulating what you have. Now finish it...