A 6.0 LS engine will indeed bolt to a 700R4 transmission.
However while the 6.0 LS engine will bolt to a 700R4 transmission, it will still require specific conversion parts to work properly.
In order for you to use the 700R4 transmission with your 6.0 LS engine, you will have to use an LS Flexplate Spacer/Adapter, because the LS 6.0 engine's crankshaft flange is shorter than the older small block engines.
And so you will need to leave one of the bellhousing bolts unfastened because the patterns for the bolts don't match perfectly.
So while the 700R4 transmission will bolt up to the 6.0 LS engine, 1 bolt hole to mount the 700R4 transmission to the 6.0 LS engine will not be used and you need the small adaptor that fits into the crank for the nose of the torque converter.
The 700R4 transmission is universally compatible with Chevrolet small-block (SBC) and big-block (BBC) engines that feature the traditional 90-degree Chevrolet bolt pattern.
This makes the 700R4 transmission a highly versatile transmission for a wide range of V8 and V6 powerplants.
Compatible Engine Families for the 700R4 transmission include:
Small-Block Chevy (SBC): Any traditional SBC (e.g., 305, 327, 350) made after 1962. Later Vortec (Gen 1+) engines also bolt right up, though they require a Vortec-compatible intake manifold if you are running a carburetor.
Big-Block Chevy (BBC): Large displacement engines like the 396, 427, and 454.
(Note: Tall-deck big blocks will fit, but building a 700R4 to handle massive big-block torque requires heavy-duty internal upgrades.)
90-Degree V6: The 4.3L Chevy V6, which uses the exact same bellhousing pattern as a small-block V8, mates seamlessly.
GM LS-Series: Modern LS engines (e.g., 4.8L, 5.3L, 6.0L) will physically bolt up.
However, to properly mate the torque converter to the LS crankshaft, you will need to use a dished flexplate and a crank pilot spacer.
Aftermarket Crate Engines: Many builders pair the 700R4 directly with high-performance crate engines built on the classic Chevrolet platform.
Incompatible Engines for the 700R4 transmission that won't work include:
Buick, Oldsmobile, Pontiac (BOP): Traditional BOP engines use a different transmission bolt pattern. An adapter plate is required to mate a 700R4 to these blocks.
Ford & Mopar: These require custom aftermarket bellhousing adapters.
Also it's also important to remember that to make the 700R4 function properly behind your engine, you must connect and carefully adjust a Throttle Valve (TV) cable.
This cable connects to the engine's throttle linkage and dictates the internal line pressure of the transmission.
If the TV cable is not set correctly, the 700R4 transmission will fail almost immediately.