go to
www.extrudehone.com and request a brochure. I ordered one and in the brochure it says that they flow match all the runners (apparently #'s 1 and 5 flow less than the others) and i think it increases flow to over 50% more than stock. Definately worth looking at even though it'd cost about $500. If you can do this at home, i believe that you can really extensively port them if you have the right tools.
If you open up the systemax lower and match the upper to it, i'm sure you could make ALOT of power. Hell, even if you port the sh/t out of the upper and make a mistake you could probably find another used one for under $50. Good luck,
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previous name: 84stangLX
'84 Mustang 5.0 LX
my LX
'89 Mustang GT
my GT