I believe you can get very close, I'd possibly look at another manifold option though rather than porting. Look at the Skunk2 Ultra Street, its already 74mm :)
The Fidanza is the only real worthwhile upgrade as its nearly 1kg lighter than stock. Depending on what clutch you buy also they may also require a skimmed/new flywheel for the warranty.
http://www.tegiwaimports.com/fidanza-lightweight-flywheel-honda-k-series-k20a-k20z-3-6kg.html
Ours are as good as OEM, so good that the UK'd top importer buy them for their fresh imports.
http://www.tegiwaimports.com/tegiwa-oem-style-type-r-stickers-honda-integra-dc5.html
You really won't like the price of genuine... this is the only way to get genuine Honda.
http://www.tegiwaimports.com/catalogsearch/result/?q=synchro+sleeve+genuine
The best option is a set of these...
They did correct the shafts and we sold 3 sets since then with no issues (correct length).
I am not sure why they have reverted back to the old design but they are now aware of the problem.
Thanks
One of the reasons to consider Yellow Speed over others is that the European warranty has now been increased from 15 months to 18 months. Thats 6 months longer than any other direct competitor brand manufactured in Taiwan - so Meister R, BC, 6two1, D2 etc