Hi Beeba,
nice to see someone else coming out of his dark ages ;-)
I have all of the models you were asking about, sadly the the 8070 is taken apart right now so I can't include it in my pictures.
Judging by the seats, which are built in almost the same way in 8258 and 8043 (both have this part as the base: http://www.bricklink.com/search.asp?itemID=923&colorID=7 ), I would say the are almost the same scale.
I did take some pictures for you:
http://www.brickshelf.com/gallery/casehase/comparison/img_0136.jpg
http://www.brickshelf.com/gallery/casehase/comparison/img_0135.jpg
If you are deciding wether to get the 8070 or the 8043, I would recommend getting the 8043, but if you have enough money to get them both, this would be the right time now, since Toys'r'Us and amazon in Germany have 20% of Lego products till tomorrow. I wouldnt pay the normal 109,99 € for the 8070, but 90 € is definitly ok. Being someone who got the 8880 as a kid, I was kind of dissapointed with the 8070 (no working steering wheel, gearbox used for the power functions instead of being a real gearbox...), but it still is a nice set anyways.
I do have more pictures, including close ups of the seats and comparison between 8258 and 8110 in my brickshelf folder:
Brickshelf