cam specs for the 420 are the same as the 525SC.
It is Crane part # 132561
Flat tappet hydraulic cam 228/236, .530/.551, 114 lobe sep
Not worth going to a larger flat tappet cam. If you're gonna go bigger, go to a roller cam. It'll cost you about another $800 to go to a roller. You have to run more expensive springs and timing chain set. It will gain another 20-30hp over the flat tappet.