The body swap would be easier, then all you need to figure out is the speedometer and the wiring. I didn't have that option because the frame was rotted on my '95. If you don't already have an LT engine, I'd skip it and go for an LS/Vortec.
My swap cost a lot more than I wanted it to because I had to replace a lot of the peripherals, and it's still a 20 year old engine with a quarter million miles. I should've sold it and got a 5.3 pickup donor.
1988 Caprice Estate wagon w/ LT1 power
1986 Pontiac Parisienne Safari 230k miles when wrecked
1990 Chevy Caprice wagon 260k miles when sold
1995 Chevy Caprice wagon 220k miles when frame broke