questions about drop blocks

[sir_talk_alot]

ok so ive got a good chunk of change coming in this week, and if i can find a place to get some 295/50/15s and get rid of the stupid 31s on my truck for cheap(get lucky and find blemished tires), i will be lowering it soon. im going with a 2-2 1/2 front, 4 1/2-5 rear drop. from talking with a few people, i can use my front shocks which are new, on the rear as my drop shocks, and buy new drop shocks for the front. im probably going to cut a full coil on the fronts to give me the 2-2 1/2 front drop(what i was told from a mechanic friend), and then after talking with shawno, probably do a 3in drop coil rear, with drop blocks. here is my ?, i was on cpp and it lists 1.5 drop blocks, and 2 in drop blocks, but says not to use 15" wheels with 2" drop blocks, why is that? because id like to do 2" rear blocks but i have 15x10s with hopefully 295/50s on them. any input is welcome and if anyone with a swb has this drop-2/4, 2.5/4.5 or 2.5/5, please post pics so i can see what it would look like. thanks! and is this all i need to lower it? i heard something about a "bar" to keep my rearend center? idk, but im not going wild with a drop, just a good lowered stance.