Well according to my brother if you get that range now you should still get that range since the receiver see's the the antenna as it was. It is still the same length as before.
Since nothing is done that can't be un-done with a simple desolder and resolder back to the old antenna mount you have nothing to loose so simple to make give it a try. You could even run the end of the black wire out one of the vents and just lay the ciol on the back deck for a test if you like the results then mount internaly and make a scale dummy antenna on the outside.
You could also make a functioning external scale antenna by removeing the the amount of the scale antenna from the coil and put the coil between the black antenna wire and the end of the scale antenna as far as the receiver is concerned the antenna is still full length