Been doing some research on the block variations
6CTa 8.3 B/S 4.49/5.31" 12V p7100
flat tappet camshaft
Splah cooled pistons..
ISC 8.3 24V
there is Caps version and swapped to HPCR in 04-05 later ISC where 8.9L
Up graded parts.. block/oil cooling system
Replaceable mid-stop cylinder liners made rebuilds easier and gave the engine a longer life.
Directed Piston Cooling lowered the temperatures which also extended the lifespan.
A crankcase breather which eliminates nearly all oil carry over.
A combination full-flow bypass lube oil filter which improves filtration, therefore, giving components a longer life.
A high-efficiency lube cooler which lowers the oil temperature but also enhances lubrication.
Roller camshaft followers that extend the life of the camshaft and are similar in design to ISX and ISM Heavy-Duty engines
ISL9 (538ci) B/S 4.49/5.69 Same block/head as ISC
Fuel/ECM are different... See alot off 2150/2250 ecm numbers on them.. I know Faulkner doesn't like those numbers.
ISC/ISL had optional Engine brakes along with turbo brakes
From ordering parts the timing gear housing for a 6cta will mount too all afore mentioned blocks same with FW housing and oil pan
Short block is the only thing that hasn't been replaced/rebuilt.. it's starting to spit oil out the crank breather under heavy prolonged throttle.
Thinking about finding a ISC/ISL block to rebuild/buy new...maybe a 8.9 version, fingers crossed nothing happened to current one till at least December 2018