First off, the Canon EF 50mm f/1.4 is not a macro lens, it is a normal prime. I believe its mag ratio is 1:1.6, so it doesn't magnify at all.
The Makinon is a 2x teleconveter, which means that it will double the focal length to 100mm if used with the FD 50/1.8 (it will also reduce the max aperture). The Makinon, judging from descriptions I've read, has 20mm of extension tube built in, which will allow the FD 50mm to focus a little closer, but not at 1:1 (life size). For 1:1, you would need a full 50mm's worth of tubes.
I'm sure there are a number of FD macro lenses out there. Check out KEH.
OR... you could just get a macro 4/3 lens. This one looks nice and is a 1:1 macro lens:
http://www.bhphotovideo.com/c/produc...arit_45mm.htmlEdited by GoneTomorrow - 1/13/11 at 7:10am