I'm certain they flow better than the two valvers, just not well enough in stock form to still do very well against a mild port and polished set of 3.4-3.5 heads according to the results of the flow tests on the 60 degree forum. Ported against ported I'm sure they would flow much better. There was a nasty debate that developed from flow results over the heads mentioned as a result of some claims made probably because someone had a difficult time believing the results. I was surprised to thinking there would be no comparison. None the less there is a .1 litre difference between the VVT 3500 and the 3400 DOHC but I believe they are both rated at 215 hp. The VVT 3500 has better flowing stock heads than the non VVT 3500 which has better flowing heads than the 3400. So one could possibly see the likelyhood of the early DOHC heads not being as impressive as what's being produced today given the closeness in power rating of stock heads.
The naturally aspirated non VVT 3500 on the 60 degree forum with a camshaft, port & polish, and headers boasts 273 hp and 259 lb/ft at the wheels and a 13.73s 1/4 mile. The 3.4 DOHC heads have a lot of potential but I would take my chances with the aluminum two valvers. I can't imagine trying to port 24 valves worth of cylinder heads.