99 Magnum Roller Cam Oil Pump Driveshaft

Stock cams (including rollers) or cams ground on stock-type cam blanks can use the stock intermediate shaft, or the MP HD shaft P3690715 (Milodon 21530 and Melling IS72 are similar).
Bronze gears are generally only needed on billet cams.
Shafts with melonized gears are offered by Hughes, HUG-6215SB- but currently out of stock.
If you already have a shaft with a pinned gear, you can buy just the gear from Hughes and mount it on your current shaft, HUG-6997.
If Howard's tells you to run a melonized gear on their particular cam, then run a melonized gear. Period.