Probably not worth trying it yourself, you'll ust get dirty and it will not make much difference unless you know what you are doing.
More important, check the valve guide clearances and plan/budget to change the guides, also have the valve seats cut with mira (or similar) 3 angled tooling, make sure you get the combustion chambers volumed and equalised, these can be wayyyyy off on multi-head engines, and are rarely that good on single head engines either!
If you want the heads ported, then I would be happy to help you out. Either with detailed advice, or by doing it for you.
Finally, don't get too consumed by percentage losses, graphs and other theoretical mumbo-jumbo... R&D and years of experience is probably enough at this level of ambition. ;-)
Cheers,
Mike.
Racing Green Motorsports