340 crank with 318 harmonic balancer?

Will do, I fell victim to the Headman header sales pitch. lol
So some parts have 1/16" clearance that could close with engine torque. (Ugh)
I'm considering the 340 manifolds and ditching the headers. But those are pricy....
I sold my early 340 manifolds for enough to buy a set of TTI's.