[SD455DJ]

Ken, maybe you know this already, but AMC’s got better designed higher flowing exhaust manifolds starting in 1971. They came on 360/401 (304 too...maybe?) engines in the Javelin, Matador, and Ambassador. They should be reasonably available, but the AMC guys like them for the earlier cars to keep the stock factory look and better performance over the old logs, so it will require some patience to find. If you are interested in going that route, I can have my AMC contacts search for some…unless you are going to use headers, then disregard this post. Here are pics from my brother’s 401 Javelin’s to compare the exhaust manifold design to yours.

Dennis

PS: Actually, these manifolds won't work...they are for the 1970-up heads with the dog-leg exhaust ports, yours has the older design rectangular ports. I missed that it was a '69 343...darn!