That would be correct. The LS engine has only 5 bolt holes for the bellhousing not 6 or sometimes 7 like traditional engines.
The other situation is that the relationship between the crank flange and the bellhousing mounting surface is not the same as a traditional engine, and you must deal with that too. And some 6.0L LS engines are different from the rest.
Rick is right for the most part, little clarifications.
The LS Gen III/IV motors have 6 bolt holes. Unlike the SBC the very upper bolt is cast and drilled and used un like the SBC. The upper R/H bolt if looking at flywheel is undrilled and not used on the LS. It can not be drilled or you will hit the cylinder.
So the Gen III/IV trans use the upper most hole. All Gen I or Gen II engines don't have that upper hole even cast in their transmissions. So if using an early trans up end up with only 5 bolts in it which is plenty.
The crank offset of the Gen III/IV motors is .400 intoward the crank. So to make up for this to run Gen I/II trans in some applications like the NV3500/4500 and 4l80's GM used a long thick flanged crank for some very early motors. Later around 2000 GM went to a common crank spacing and used with a dedicated flywheel with correct spacing or a spacer for the 4l80 trans applications.
And SBC pattern will work with an LS motor.
Now the LS4 is unique as it was a front wheel transverse mounted motor which has a 60* V6 bellhouse and is the only LS motor built like that. It lacks provision for a starter mount pad so it is a very poor choice for swaps.
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