The Prime Directive of Amtrak (and VIA) travel:
“Never schedule a connection to another carrier on the same day as arrival of any North American long distance train.”
The train could run on time or close to it for weeks on end and then your train runs into some idiot at a grade crossing, delaying it by hours and blowing your connection.
Past performance is not indicative of future results.
Save time, forget this ongoing monitoring and just get the train's statistics right now. Run the history of the SW Chief's actual arrival times at LA on ASMAD
https://juckins.net/amtrak_status/archive/html/home.php. Then reschedule your Amtrak reservation. Modifying the date
will be at current bucket, probably a small price to ensure you make your cruise.
Otherwise you might just wind up eating Dinty Moore over rice around Barstow and thinking about your ship that just sailed away.
It has been more than four hours late 29 times since January 1st. That means about 1 in 6 trips. Four hours late is more than enough time to endanger your cruise since you have to get to Long Beach or San Pedro, roughly 25 miles away from Union Station, in LA traffic. Cruise check in cutoffs are absolutely inflexible and are usually at least a couple hours before actual sailing.
The SW Chief has been as much as 15 hours late since the first of the year.