what the lowest
 

i got a 07 sliverado what to drop it but want 24 inch rims what the lowest drop i can go and fit 24

Depends on what tire size you go with. With 24's you're pretty limited. Unless you trim out those fenderwells.

well like the above post said you will have to cut fender wells if you get to low and too big off tires
if not you will cause tire rub which will eventually turn into a tire blow out and or front end problems
i would suggest tirerack.com they can help with tire fittments and i believe the have a section on how low you can go with certain tires or i woul just call a suspension shop and see what they have to say but if they tell you to bring it in call another place cause they just want money if they say bring it in to have us look at it

if its the new body style you should have no problem with a 3-5 or 3-6 drop "if" you dont go to big with the tire size. i have 3/5 with 295 series 26s and only minimal fenderwell mods

The offset of the rims you go with will also be a determining factor on whether they rub or not also.

Find that tire shop that will work with you to find that perfect tire and rim package for your truck.
A good tire shop will try different set ups before a final bill is paid.