The factory 8.8 posi rear end will be fine if it meets the width requirements. I think it might be 3" wider than your original, wheel to wheel. Depends on the wheels you want and the ride height.
Cable clutch is preferred. Pedal is easily adaptable.
Trans mount is about 2 inches farther back, I think.
The '90 up has a slightly stronger rated transmission.
Use the modern yoke and u-joints when making a driveshaft.
As you surmise, the engine swap is easy. The wiring is a piece of cake.
The brick should easily get 22 on the highway with the A/C on.
But you must realize that the stock 5.0 makes 260 hp on the engine dyno, and about 225 in the chassis, and about 195 at the tires. But it is geared well with the 3.35 ratio first gear. More than 3.55 in the differential gets too low for using first gear on the street. 11.89 ratio!
Been there, done that, several times.