motor drop how much??

hey im doin a 3 1/2" BD and i was wondering how much i need to drop my motor ie got a weber carb and a 2600 hood will cut out support on hood if needed or thinner filter for weber if made
oh yea and do all that i do is dop the motor mounts down right?

if i get that thinner filter from weber will it help much or just make me lose power?

mine is bd'd 3 inches and i have the weber carb and the filter it came with and a 2600i hood and i don't think i have to drop my motor at all but i'm going to about an inch