I have a set of 302s on my Barracuda right now, that's why I have the original '69 heads on the shelf. As far as the manifolds are concerned, I would sell them to you unpainted (so you can get them dirty and it won't matter). Then if they don't work and you don't damage them I'll simply buy them back. If they do work you can keep them. I keep these manifolds in stock so I don't mind buying them back, it's kind of a hobby. But take your time and read through all the posts on the thread. I've built up my stock of manifolds for the coming spring. Most of the buyers are up North (and Canada) and those folks don't build nearly as much during the winter so I stock up during the winter and sell in spring and summer. Here are some pics of what I keep in stock. Actually I have more than what you see in the pics but it's too much trouble to haul them all out into the sun then put them all back just for a few pics.
And remember....you would be trying the 60s 340 driver which gives you more clearance than the 70s 340. They flow the same but the 60s is designed for more clearance. The 70s 340 would probably not work at all!!!!