well, the original poster did mention getting 302 heads for it in the original post. if he is thinking upgrading heads, the best bang for the buck will be a set of OEM magnums, because you also get the added bonus of 7% more lift on the same cam due to the different rocker ratio.
looks like he already bought the '77 318, so that is water under the bridge. personally I would have sought out an '85-up 318 or a magnum 318 as my base to build because of the OEM roller cam hardware, and in my experience, regrinding the factory roller to something a bit more aggressive was less expensive and more reliable than a flat tappet cam cam and lifter package.