I gotta admit, 3 months ago, to me all this suspension talk sounded like the equivalent of the adults in the Peanuts cartoon talking amongst themselves.
I would recommend the 3/5.
Now that I'm edumucated thanks to alot of reading and guys on this board, I'd say you're almost definitely going to have to cut of the bump stop brackets from the frame in the rear. The truck will end up settling down on the bumpstops or damn close to them and you just dont have enough travel, so the ride will be stiff and every bump felt through the truck because of the axel riding on the stops. I cut my bracket and actually ended up putting aftermarket bumpstops on the axle piece that marrys up to the frame on bumps instead of the frame itself. Was easier that way for me.
For the front, you should be very careful when you are trimming the bumpstops in my opinion - you don't want to cut them too short. That's what my installer did when he did my front spindles and keys, so I had to find some new bumpstops and reinstall them. I ended up not trimming them AT ALL, and my front barely rides on them 100% of the time. My front bumpstops are from a S10 Blazer (junkyard) I think, they looked newer/stiffer and just the right size to keep my **** from bottoming out any more.
HTH
BOSS