Accurate HO tie plates are already etched and avialable from the Proto:87 Stores - and can be easily cut for cosmetic attachment to existing trackwork.
See:
http://www.proto87stores.com/p87stores/frtrck.htm#ULTIM
Available in old, modern styles - can be fiteed to codes 40/50, and 70/81/83. Alos check out the variety of proto and larger (but smaller than other suppliers) spikes - same reference page.
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-ed mccamey-
COSLAR RR -
http://www.coslar.us/NMRA Standards and Conformance Department
PROTO & FINE Scale Coordinator
I estimate I have about 5 pounds of coupler springs somewhere in the vicinity of my workbench.