A little advise

With what everyone else has said above plus.....
If you are rebuilding, then the 413 can be turned into a 440ish type engine. If not, the 413 starts out with low compression. If your changing the heads, I would use 915's, 519's or one of the ProComps aluminum to boost the compression. I would use a thin head gasket also. Many of the Comp cams packages compliment this build, so cam selections would follow knowing head type (compression), and intake.

K-Frame - I like spool types, they are cheap (low budget) and provide a little more room and strength(not much -and this is my opinion form past experience). Schumacker ( sp) makes great mounts for all K frames- easy to use and reliable. Shumacker also makes a good header for this build. Recommendation would be to grind the weld coming from the head to make a bit better flow.

My 2 cents