You really stuck your foot into this one Bruce, now you are going to be stuck answering stupid questions for the next couple of weeks.

The Fiberglass Shell as the OP called it is called a Radome.

http://en.wikipedia.org/wiki/Radome

The problem the OP has - besides being cheap and wanting something for nothing is the fact that he does not understand what is inside of the radome.

If you disassemble and Antron A99 or a Diamond X 500 - once inside, you will find a piece of copper wire or steel wire or stainless steel wire that is usually copper plated.
Between each section - spaced for certain wavelengths is capacitors of unknown origin which makes the antenna into segments - some for 2 meters and some for 70 CM.
This is what gives it its gain.
These are purpose built antenna's for those frequencies..

You cannot take a Marine antenna - that uses a different frequency and use it on amateur frequencies - due to the fact that there is no way to get internally inside of the antenna and change the lengths of the segments of the wires inside of the antenna.

Unfortunately - there is not a lot of educated Elmers out there that are willing to help a newbe - just due to the fact that most of the people who are left in Amateur Radio came from the CB radio and they were not knowledgeable - like the ones who came before them.

Most of them never built anything in their life and are just appliance operators.

I believe I had this conversation with this person or another person like this person previously.. My advice was that if the threads are of a ******* Origin and you are not willing to repair them or buy the mount to throw away the antenna..

They do not make a tap and die or make one that is economically feasable to repair a $10.00 antenna.. When you get into non standard threads - if you can find a tap and die - they tend to be quite pricey..

We are talking $60 - $100 each...

You would have to fix a whole bunch of antenna's just to break even, and it wouldn't be economical to buy it to fix one antenna.
You could buy a Diamond X 510 for about $150.00 and it would be already designed for the frequencys you desire to operate on.

JMHO
CJ