what needs to be changed in a 72 340 to be like a 70 340?

rumblefish360 said
tti headers are the ones you want to make the HP you seek. Otherwise, the exhaust manifolds will hold you back 70+ HP.

I thought it be more like 20hp. I know those 1970 hp cast manifolds can allow for some decent flow. I was running them on my 318 with 360 heads and 3.90 gears. Switched from cheap headers, notice a slight drop in power.