Most likely will be better off to buy these new, there isn't anything realistic available as an upgrade for these, trick flow makes some oem style and Jesel makes a set but they are $3600 and not worth the bang for the buck.
I made a cheap set for my 4.6 DOHC by TIG welding up the oil holes in the rocker body,then machined a slot to direct the oil and made the hole 1/32nd (i think,not sure,but a lot smaller than stock).The oil is now restricted to stay in the cam journals and what is bled is a straight shot to the cam/rocker bearing,worked great.I just tried to copy the set on my 500's engine with the 4.6.
I'm building an engine for my Lightning and bought a set of these from Tousley with the thinking that I was going to run a set of Trick Flow 2V heads but have since changed my mind to a set of GT500 heads and manifold.
I will be buying the SVT valve train kits for the 4V heads and that leaves me with an extra set of rockers and adjusters.
I'm going from memory but I know I paid 209.00 for the adjusters and I think the rockers were around 260.00 and then there was shipping.
I would sell the 16 GT rockers and 16 GT hydraulic adjusters for 450.00 shipped.