Welcome aboard. I have a '65 Cuda with a 360 and power steering and have been told repeatedly that HiPo 340 or Dakota manifolds will fit. They don't. I find that out after spending a lot of money. I don't believe anything I read on automotive forums unless someone actually posts direct confirmation and photos. There's just so damned much "Oh yeah, that'll work" from users that sound authoritative but are actually clueless.
For a long time I wanted a set of Doug's or TTI headers, but they're such a pain for a daily driver or weekend fun car. They just get in the way of everything. For example, when my starter eventually goes I really don't relish the idea of removing a very difficult exhaust system.
At present I'm stuck with 273 manifolds, which are the only things that actually fit as far as manifolds go. They make splendid rev limiters and choke the engine quite expertly.
I'm very interested to see how your DD8 experience goes. If they work, they're less than half the cost of Doug's or TTI headers.
In the back of my mind I wonder if swapping out the power steering gear with a Borgeson unit will give me the room I need for Dakota manifolds, but fear to ask. It seems like either spend a grand on a fanboy header system or a grand on a power steering gear.
My eyes are looking your way! Can you post any pictures?
