Can't help you much on the GT3 front, only have ridden in one on the track. As for the 70-73 hotrod it is important to know about the 915 transmission. If you have not driven one, they can feel "ponderous" compared to the g50 ('87 on) and later transmissions. You can certainly spend $$ to address that "feature". I really don't mind it, but some people HATE it. Might be a good time to buy, as longhood hotrod cars seem to be cooling in prices right now. Nothing like the 930 price compression, but still a cooling (see the Marketplace forum for more discussion).
I really dig lightweight longhood hotrods. If you can find one with a 3.6 swap you can probably save your money on the GT3 purchase. You won't feel the need.
