Most NA cars are picking up 20-25rwhp with cams and a tune. Cost effective? Well, thats a choice each person has to make. mod motor parts arent cheap. I picked up 15rwhp/15rwtq with a set of cams, and the curve was great. Oh yeah, this was untuned. I proboly would have had another 10hp with a tune. As far as an ohc motor limiting the rpm range, thats simply not true. Many of the top NA guys on my ET List ( http://forums.stangnet.com/showthread.php?t=727174&highlight=stangnet's ) shift there cars at 64-6600rpm with the stock bottom end. Bill Putnam(Mustang92) and the fastest bolt on 2v car to date, picked up .3 tenths with vt stage 1 cams. It might shift the powerband slightly higher, but thats where getting a low gear in the car helps.
As far as reading magazines, dont bother, they are a waste of time and very biased due to the parts and companies that advertise there.