I have a1987 f350 carb motor with a bottom end knock. I can get a good 1995 efi bottom end. Can I just swap my 1987 top end into the 1995 bottom end without having to modify anything?

 

Where is the fuel pump on the '87? (I've never had an '80s truck with 460, only '70s cars and '90s 7.5L EFI trucks) '70s carbed cars had the fuel pump mounted on the timing cover... EFI truck timing covers don't have that option. EFI engines also do not have a fuel pump eccentric mounted on the cam gear.

Not sure when the 460 changed from internal- to external balance, so use the harmonic balancer hatchet spacer and flexplate/flywheel from whatever shortblock you use.

Carbed 460s used a 22cc dish piston and 96cc heads for 8.0:1 compression , 88-92 used a 8cc dish and 96cc chamber heads for 8.6:1 compression. 93-97 used a .020-taller piston with a 15cc dish but a slightly smaller 91.5cc combustion chamber, so compression ratio stayed at 8.6:1. The F3TE piston/head combination promoted swirl and the tighter compression height (squish) lowered the chance for detonation. Your proposed '96 shortblock with earlier heads will pretty much mimic the 88-92 8.6:1

The EFI truck engines also used a 'straight-up' roller timing set, unlike the '72-87 carbed 460s that used a retarded crank gear.

 

Wow, what an assumption on my part, thinking you were asking about 460s. I first should have asked what motor is in each truck.

BUT the same goes for 351W/5.8L engines. Timing cover/fuel pump location. Same issue with fuel pump eccentric on camshaft gear.