Hunt Amplification will convert your Silverface Fender amp into its Blackface counterpart, or somewhere in between. Enjoy the famous tone and feel of the earlier Fender amps without spending a fortune on the real thing.
Actual modifications depend on the specific amp and your desired tone. For instance, many early Silverface amps do not require any changes at all, but some of the high power ultra-linear models can't be converted all the way to true "Blackface specs" without extensive surgery.