So many things determine valve-to-piston clearance issues, such as the pistons, the heads, cam lift, cam duration, lobe separation angle, valve head diameter, etc.
In a 1984 460 with D3VE heads, the OEM stamped steel rocker arm valve train can handle perhaps 0.550" lift max, assuming you have the proper valve train components to go with said cam (correct springs, retainers, locks, pushrods, etc).
If you simply want to install a bigger cam into an otherwise bone stock 1984 460, then I do not recommend a very big cam unless the rest of a rebuild is planned along with the cam change.
But if you must install a mild RV cam & lifters into a 460 with no other changes whatsoever, then I would recommend a Summit Racing SUM-3500 or SUM-3501 in your case. Those cams will work with an otherwise complete OEM valve train, offer a power increase, and a noticably throaty idle.
The Long of It...After months of reading, this is the only post that stays within a reasonable margin. I have an assumingly stock 460, that was rebuilt, and the builder indicated the engine was shut down during the initial 20 minute 2200 rpm breakin. I've taken the truck to 3 different garages, with guess what, 3 different speculations. First off, NAPA, wants to replace heads, carb, intake, all based upon low compression on the #5 cylinder. Hmm, if the lifter is stuck, and obvious tapping from the cam on the stuck lifter is heard? Lets replace everything besides whats wrong with it. Second place, which charged me 75.00 to take off a valve cover, said my valves are too long due to hard starting. Lets see, running the truck at 65mph for about an hour to get to the garage, with undetonated fuel priming the cylinder, and hard starting, one would never imagine.
The short of it...went to Summit Racing, opted for the 3500 Cam and Lifter Kit. What I'm hoping for is a truck that runs, with better than stock sound, that will pull a few things (1 ton rear end), and leaves a red light without stumbling. Highway? 4000RPM dont know how loud it will get, or if 4000 RPM is plenty.
Any advice on intalling will be greatly appreciated.