Myself, I would build the roller engine. Almost all of them during the era have AC units attached and part of the serpentine setup so that would fix that problem/issue/desire, along with the power steering.I would also stick with the Magnum heads, they breathe really good when ported and are a whole lot cheaper to obtain, and on the 318 the intakes are already 1.94s, so that takes care of that issue, being too small an intake valve for the 318s. The reason I would take the roller cammed engine, the profiles are so much better and last better, better ramps, less wear and friction. I think the Indy heads would be a little overkill, even though 2.02 valves will fit inside a 318 bore, if you know porting why waste the money, you can get your 350hp out of the engine with cast iron heads, but remove the sharp edges inside the combustion chambers and you can go easy 11:1 compression and run 87 octane without a problem. I figure you are going old school intake and distributor, a medium and light spring in the counterweights of the distributor will get you the curve to prevent any pinging, have been able to do 13.3:1 on 87 octane without a problem. If the engine you start with is complete with everything but intake you don't have to worry about the covers, etc., she will be complete and as far as I know the flex plate will attach to the rear without a problem for the RH transmissions, there are shifting and overdrive kits available to use them without the computer. Hope this helps.