The coolant capacity is chassis dependent, i.e. the size of the radiator and associated plumbing in addition to the amount of coolant held within the engine itself. You need a Dynomax chassis number rather than a Cummins capacity number.
There are a number of articles and videos for the Dynomax available online. Maybe one of them has the info you need. You may even find a chassis owner manual for the Intrigue - Country Coach produced some excellent documentation for owners.
Here's a chassis manual for an Inspire, which also uses the ISL (or Cat C9). That should be in the right ballpark.