I think the spring they recommend is about 120 on the seat. Needs to be a little more hefty than the OEM/901 because of the aggressive grind profile.
98412 is the howards part number
Howards catalog
[URL]https://www.howardscams.com/sites/default/files/Howards_2024.pdf[/URL]
Footnote says can't use stock springs with that camshaft.