could use your input please!

[hhracing]

I am desperately trying to sort thru lenses. I have a minolta max 5 and needing a a/f zoom lense for it. I shoot driver photos for the local gokart track and I have been using a tokina (older) 70-210, get great pictures, focus ok when I have sunlight, but horrible when I dont/look worse when pictures are blown to 8x10! I cant afford the 2.8f lenses, so if someone knows of a good 70/80- 200/300 a/f lenses that would work pretty good for what I am doing would really appreciate it. I shoot anywhere from 30-100 ft away, maybe this isnt the lense I need? I know mabe asking to much for alot less, but at least maybe get close.
thanks
Terri