I used a couple of Microwave Associates relays for the antenna switch. They have extremely low loss, switch over quickly, and can withstand the power levels developed by the amplifier.
These are no longer made, but similar units are available from a number of sources. New ones sell for around $100 each at the time of this writing, so if you have them already, or can trade for them, you can save a bundle here.
The mounting brackets are made from .060 aluminum scraps.