That's what I'm most afraid if the front ifs diff. And also will i need to send my computer off for the transmission?
I am in the process of doing "all of this" myself.
To start, the absolute most important thing you can do is swap the 10 bolt rear diff for a 14 bolt. During this time, it would also behoove you to go ahead and add disc brakes in the rear. There are plenty of 14 bolt 6 lug axles out there w/rear disc brakes.
Believe it or not, the 1500 front IFS isn't really a weak point in our trucks. It can take "quite a beating". So before taking the time and energy to swap it out "just because", I would put your money elsewhere.
The two most important changes you can make are:
1. Rear axle change 10 bolt to 14 bolt.
2. Transmission upgrade.
On the transmission, yes the 4L60 is really weak for high hp/torque applications. But, you can go to different routes which will save time and money.
1. Rebuild/upgrade it to 4L65
2. Buy a new upgrades tranny from Road Ripper or Monster Transmissions.
I personally would not put a used 4L80 in the truck. Not because it isn't a good transmission, but you don't truly know how well it was taken care of. With that said, it can be done, but by the time it takes and the money you spend doing it, your almost to the point of a new upgraded 4L60/4L65.
I've been on the fence on wether or not to put a 454 or stroked out 502 in my 2 door. After tons of research, I'm going with a 400HP 383 Stroker, which the computer will run, an upgraded 4L60 from monster transmission, 14 bolt axle. That's as close as I plan to go with a beefed up drivetrain. Hope this helps. At the end of the day, it's all personal preference but I thought I'd share my two cents. Good luck