Makeshift Model TA ?? What is it exactly?

OK, now what exactly is a "Makeshift Model TA"? I know its a big Brady Bunch hit, but what actual car model does the "TA" refer to? Is it a type of "Model T"? A Pontiac "Trans-Am"? And if so, what about it is so bloody "Makeshift"? This is very important... show more OK, now what exactly is a "Makeshift Model TA"?
I know its a big Brady Bunch hit, but what actual car model does the "TA" refer to?
Is it a type of "Model T"?
A Pontiac "Trans-Am"?

And if so, what about it is so bloody "Makeshift"?

This is very important stuff, you know ;-)

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http://www.lyricsbay.com/keep_on_lyrics-...
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