be sure you want to chop AND channel it, that really limits how much room there is inside the cab and you might not fit or be very comfortable.
what frame are you going to use?
I like to Z the frame instead of channeling, it lets you keep interior room but still lower the truck.
as far as the chop, I dont know what you mean to "keep the door glass orginal"???
doing glass for that truck is easy as its all flat glass.
when you do the chop, lets say you chop it 4" then you will have to cut across the top from door to door and add about 2-2 1/2" so that the windshield area will line back up.

check out how I chopped the racetruck in the link below to see what i mean. Ron...


http://rides.webshots.com/album/559598861LBwiIz?start=24