FWIW: I used a set of 1985 194 truck heads from a 350CID. Before I used them i turned them into 2.02/194 with stainless valves and LT1 springs. I used felpro head gaskets specifically for a small block 400. You MUST drill the steam hols in the heads for the 400cid application which I DID. I kept the rocker arm ratio stock (1.5/1) but went with the roller tipped stamped rocker arms. A 268XE cam works really nice. Lumpity, lumpity, lumpity.
A holly 3310 sits on top.
I agree with the rest of the guys, the 400 is an awesome motor. Mine lays some pretty *****'en scratch marks. BTW my slush bucket is a built THM400. I can beat on that thing all day. Final drive is 3.73 12 bolt.
Summers coming; Happy Cruz'in.