alright i'll give u my specs, i usually run in excess of 100fps, with everything maxxed out.
1.8ghz dual core Intel
2gb ram ddr 800mhz if i remember correctly, soon to be 4gb
Windows Vista 32 bit
Creative X-fi Platinum
XFX Nvidia 8800gt 670mhz GPU
Gigabyte mobo with intel chipset (can't remember what model, its out of production now)
This setup will EASILY cope with LFS as it is atm, even with loads of cars on the track, it only drops to 30fps with a full grid of cars, i usually run an mp3 player in the background for music too. I think with a different video card this setup was like $2500AUD about a year ago, so a cheap system should be a cinch to play LFS. Good luck.