Joe, Joe, Joe,
OK, saw your other post on heads....
Your 292 oval open chamber heads are fine....
8.5:1 CR 240 horse/345 ft lbs torque NET ratings with accessories, right?
Everything is relative....cost and time.
Cheap is to re-use what you have...it is a runner, right?
Have a 3-angle valve job done by a reputable shop. Have them install springs to match your cam. Get some bowl clean-up under the valves.
Have them shave the heads a bit to true them up and also decrease the chamber size.
Run a shim head gasket like the MR GASKET 1302. (think this is not right...1131 IS the right number) They feature .018-.020" compressed thickness compared to most head gaskets which compress to about .040". You will have to apply spray-on sticky stuff and you will have to re-torque the heads after you fire the engine.
Shaving the heads and the shim gasket will bump your CR closer to 9:1
Let's use the KB compression calculator for the 402" piston KB-160
http://kb-silvolite.com/performance.php?action=details&P_id=105
119cc chamber is 8.5:1 (caution here, chamber size varies)
115cc chamber (equivalent of shaving the deck and the shim gasket)=8.8:1
Now take the small chamber 385206 head from 1966 era has 97cc, shaved to 95cc no issue.... CR comes out 10.6:1
Roughly 4% per 1 pt in CR.....10.6 - 8.5 = 2 pts, 8% increase
Figure 300 horse x 1.08 = 324 horses....gain of 24 horse. You can really feel that.
Thing is, high compression/small cam combo means detonation.
Probably a better gain from the compression is that more CR supports a bigger cam, no soggy bottom end. Low compression/modest cam; medium compression/healthy cam; lotsa compression/stupid cam....
So, cheapest route, fix your 292 ovals...run a modest perf cam....
hmmm, small solid preferred....
No time now to go looking for cam grinds.....
Modest compression, 3.08 gears...street, limited rpm...
Something solid 225* roughly at .050" lift, lift will come out at .520-.540", 108 LSA
Though a smaller Voodoo Hydraulic 60201 or the Summit brand hyd 1301 (same as the Edelbrock Performer cam 214/218* .500/.500" 114 LSA) would work well....