Hey McQueen!
The part number I gave you from Summit is a kit that includes the lifters. As to rockers - I believe in your class you can not go with rollers and I'd stay with the stock rocker arms - tried and true GM stamped steel. Vortec heads are good for .450 and this cam will work fine.

Installation is critical and the lifters must be properly seasoned/broken in at initial start up. Follow these instructions:
Make sure you soak the new lifters overnight in oil and then lube the new lifters with the supplied grease and slide them into the lifter bores. Next install the pushrods through the cylinder-head holes and loosely install the rocker arms with the pushrods against the cups in the rocker arms. As a part of this step you should check the pushrod length. Mark one of the valve tips with a black Sharpie before the rocker is installed and rotate the engine by hand a few times. Remove the rocker arm and examine the valve tip. If the rub point is in the center portion of the valve tip, the pushrod length is okay. If the rub mark is closer to the rocker stud, the pushrod is too short. If the rub mark is at the far side of the valve tip, the pushrod is too long.

To adjust the valves, rotate the engine by hand several times until the intake lifter of the number 1 cylinder begins to rise. When it reaches full lift, tighten the exhaust rocker until the push rod is tight as evidenced by the lifter plunger just ever-so-slightly begins to move. Slowly tighten the rocker nut 1/2-turn. You want to pre-load the lifter but not bottom it out. Continue this process across the engine, lashing the opposite rocker (same cylinder) of the one at full lift. Then you can put the manifold and valve covers on and finish the little things necessary to and start the engine – distributor, fill the radiator, etc.

Critical is that you follow the instructions that came with the cam. You must run the engine at 1500-2000RPM for 20 minutes to properly condition the cam so make sure you have enough fuel and that you have the time to do this. If you start and stop the engine multiple times, the cam may be ruined.

Have Fun,
Glenn