99 Silverado with stock 5.3

[ff_jeff]

Oh ok u meant "drop". Lol. So use the 5.3 accessories brackets and intake on the ls1 and order the 5.3 supercharger. So the ls1 heads have the same bolt pattern as my 5.3?

yep. The only real visual difference from a distance will be the color of the block. And up close the head casting numbers.