OK what valves to use, I found these three from a quick search on Summit
http://www.summitracing.com/parts/slp-v-2143/overview/make/chevrolet
http://www.summitracing.com/parts/man-11506-1/overview/make/chevrolet
http://www.summitracing.com/parts/man-11542-1/overview/make/chevrolet
There is a huge difference in price, will there be any real difference in power, or longevity? Are there better valves/values?