Deciding on replacement intake (318, details in post)

I feel like at your current power level, significant gains could only be had with a "complete package" rebuild, at least in regards to cam/heads/intake. IMO going from cleaned up and milled J heads to unported Trick Flows will give an incremental boost, maybe 30 HP? If it were mine I'd go for some heavily ported Speedmasters, get that intake flow up in the high 200s CFM range (at least). You're at the point in the "Cost vs. Power" curve where it starts getting a lot more expensive to make solid appreciable gains in performance.