Eliminating income tax would just mean that another form of taxation would take its place; the likely candidates would be large sales tax, increased corporate income taxes, luxury taxes, estate taxes, increased capital gains taxes, and carbon taxes. Some of these taxes would have very negative impacts on the ecconomy while others would be far more neutral in effect.
Eliminating the Federal Reserve and moving towards a gold standard would put the US in a very tough position in the global ecconomy. Because most of the developed world uses floating currencies the exchange rate between the US dollar and other currencies would vary widely depending on the current state of the world ecconomy; this would cause instability in the US ecconomy which could potentially result in overall lower employment and productivity.
