318 camshaft swap 260 duration

It should work well with your combination. It has pretty fast rate lobes and might be a touch noisy. With exhaust manifolds and not headers, a split spec cam usually works a little better. There is more duration and lift on the exhaust side to make up for the manifolds. @RustyRatRod recommends Comp's 255DEH COMP Cams Dual Energy Cam and Lifter Kits CL20-416-3