Littelfuse 257 ATO is now obsolete according to their website and has been replaced by ATOF 32V series. Not sure which model Bussman you are referring to but it is most likely the ATC 32V model.
I looked at the fuse time current curves and they are pretty close, not enough to make a difference in this application.
I would go with the least expensive ones.
2016 Chevy 2500HD Duramax LTZ Z71 double cab long bed
2012 Dodge Ram 1500 5.7L Hemi (with K&N Air Intake) (traded)
2012 Rockwood 2109S (SOLD)
2014 Cougar X-Lite 21RBS
His & Hers 2016 Vespa Sprint 150's