Last August, I got fed up with the Chevy 350 that came in my '67 GTO when I bought it. In September, the 350 was pulled from the engine bay.
As of this past Saturday, the GTO is on the road again with a '67 400 under the hood. It's been a struggle - since September, I've gone through 3 different carburetors and a cam swap when I discovered that the Crane Fireball that came with the motor had a bad lobe. The final specs came out to '67 400 YS block running dished pistons, '68 #16 heads, '68 intake, 7028268 quadrajet, Summit 2801 cam, '69 timing cover + water pump, Ram Air Reproductions oversized ram air manifolds, 3.36 positrac rear end, bolted to a TH400 with what I'm told is a 2100 rpm stall.
It's not perfect - something seems a little off in the timing, as I have to let it idle out of gear at around 1300 rpm to keep it from stalling out in gear, but there's a world of difference between 'barely running at all' and 'I can at least take it down the street'.
This friday I'm going to have the exhaust hung - but for fun, here's a quick little video my parents took when I left their house in its current state, running nothing but turndowns off the manifolds.