A real Hemi in race form will run you close to 20K by the time you have it all in and running and they are a high RPM piece, A big inch small block would be a lot less expensive. I know since I race both.
How much spring you will need is in part dictated by the shape of the cam lobe (profile) and RPM. You could always go to a little less rearend gear also,lol.
A pair of Holley 1850s (600cfm) would look correct and can be bought used super cheap. Or I'll sell you a new pair of the correct 770s and repo fuel lines for $1200.
I skipped a few pages in the middle but it sounds like it wants a little more valve spring pressure. A .060 shim might be enough to do it. My slant liked 32 degrees total timing also.