Need some suggestions!

I would be inclined to go to the 262H after going back and forth. Either will likely match up about the same with the stock TC, but the 268 will tend to be a bit softer at lower RPM; that would make it less likely to break the wheels loose, which is going to be any issue with this truck's light rear axle. But the higher lift of the 268H may give problems with the retainers hitting the valve seals. The 262H is a safer bet there.

Agreed on the springs. Changing them in the car is not such a big chore. You can research retainers at the same time.

You need to make an investment in the brakes and front suspension when you do this; this thing is going to be able to do some pretty high speeds.