first off you don't need forced induction to get into the 12s it is one way but you can get there with all motor as well

use the afr heads, if you are building the bottom end use the large chamber heads and pop up pistons, but if you are planning on keeping the stock bottom end get the small chamber heads as they will up the compression, do you plan on keeping it fuel injected or going to a carb? i don't know much about how to make these fuel injection systems on these trucks perform but....i do know how to build a motor with a carb, put on the small chamber large runner afr heads with a stock bottom end (low mileage that has good compression ect. ect.) and put on a good intake like an rpm airgap or equivilent port match the intake to the intake ports on the heads and port match the exhaust ports to the headers for the cam go one size bigger than what you think you'll need because you will always wonder what it would have been like with a bigger cam and that also allows some room to grow before you outgrow your cam and have to buy a new one and if you just build the motor and don't put a stall converter on your trans you will be dissapointed, i don't know what trans you have but i know with an e4od you'll want to keep fuel injection since it is all tied into your engine computer somehow, with an aod you can run as much stall as you want and still have it streetable since in third gear and in overdrive it locks out the converter unless you have a one peice input shaft (never came factory) but what ever trans you have get it so the stall is right about 100-200rpms above the advertized powerband of your camshaft that way when you launch it you will be right in the powerband, as for the gears i am sure you have an overdrive trans since i don't think you could get a 150 with a c6 or c4 and 351 so since you have overdrive you can probably run 4.56 gears with a 31in tire or so and be at about 2000-2800rpms on the highway at 60mph which is where i usually gear all of my cars to except for my truck because i would have needed 4.88s instead of 4.56s and with 4.88s i would be breaking way too much stuff, now i really doubt you'll be able to get that truck to hook with drag radials and a built motor so i would just invest in a set of slicks and have a set of street tires as well and use the same front tires for street and strip (get skinnies it really does help on the topend with friction loss compared to wide front tires)

try playing with removing the front sway bar and see how your truck likes it, i know my t-bird hooks better without the front sway bar but i also know of some cars that like the front sway bar

if that setup doesn't get you into the 12s then start to do some weight reduction such as remove the heater, smog system, air conditioning, inner door frames, inside tailgate skin, lighter rims, fiberglass front end, pull the gas tank for a fuel cell mounted in the bed. that's just the weight reduction which most of it you can make money from by selling the parts you take off and using that to fund the weight reduction parts like the fiberglass front end and fuel cell...ect remember every 10lbs saves is a tenth of a second (just rule of thumb)

if that still doesn't get you to the 12s buy a wet nitrous system (if you go carb. get a spray plate) and remember every 10hp is a tenth of a second