john,
i think the difference between the two are as follows:
the cheaper one is a universal antenna and it says it works off the power knob of the radio. it maybe for an aftermarket radio i would suspect as they have a separate wire for antenna. on older cars the power goes in thru the plug which is constant power. if you look at the schematic the antenna has a full time positive and ground and a blue wire that when twelve volts is applied it raises and when taken away it lowers. you could use this one on an older radio but you would have to put a switch in to turn the power on and off to the extra blue wire.
the other is a replacement for original which on older cars used to have something like a window switch to raise and lower them. push one way to raise the other to lower.
you can use the cheaper one as long as you put the switch in. i would rather have that on anyway as you would not have to sit and hold the switch until it raised fully or lowered fully as you would with the other.
i have a similar problem like tux. i bought an electric antenna for my 75 off of ebay just have gotten a round tuit to install it. you should appreciate this one. while cruising thru ebay for corvette parts i came across the electric antenna and it was being sold for about $75.00. hemmed and hawed about buying it and while cruising thru parts for a different make car (one of my caddies), i found the same exact antenna being sold by the same guy for about $32.00 and he even sent an email explaining if you were going to install it on a vette. i bought it at $32.00. some just raise the price because it is a corvette.
by the way, one of the things in the email for hooking it up in a vette was to make sure you added a ground wire to the mounting plate. if i come across the email ( i have it somewhere) and you want it let me know.
eddie208752008-02-17 21:06:20______________
LIFETIME MEMBER #97
THE DYNAMIC DUO
I do this on my car so I can put the cover on it. I just lay the mast across the luggage rack when it's in the garage, but stick it inside the car when I'm traveling. 
) and ordered a new fixed antenna kit. 
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