If you can shoot for co-processors, there WAS that 68008 card you could build for the Apple II.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDQQFjAA&url=http%3A%2F%2Fwww.harrowalsh.de%2FElektronik%2FAPPLEBOX%2F68008CPUcard%2F68008translation.pdf&ei=X6QtUfWbOOWliQLLlYGwBg&usg=AFQjCNGVz9aHt2dv6mUB-93ZUzwFE8Uy4g&sig2=MFXycrtsxtxGjR22TZQuKQ&bvm=bv.42965579,d.cGE&cad=rja
It's all 74LS logic and the MC68008 is amazingly cheap on ebay. They even include etch templates so you can fire them off to the etcher of your choice for a nice authentic board.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDQQFjAA&url=http%3A%2F%2Fwww.harrowalsh.de%2FElektronik%2FAPPLEBOX%2F68008CPUcard%2F68008translation.pdf&ei=X6QtUfWbOOWliQLLlYGwBg&usg=AFQjCNGVz9aHt2dv6mUB-93ZUzwFE8Uy4g&sig2=MFXycrtsxtxGjR22TZQuKQ&bvm=bv.42965579,d.cGE&cad=rja
It's all 74LS logic and the MC68008 is amazingly cheap on ebay. They even include etch templates so you can fire them off to the etcher of your choice for a nice authentic board.