Sorry 820 heads not 840. Also TRW makes a forged piston for the 4.155 bore. It has a .360 dome but it could bring you to around the 10.25 comp mark and you will probably need more cam to bleed it off. I'm told with 119cc heads it brings you to around the 9.5 mark. Don't know the part number.

If you would like to install that 292 in a low compression eng, give the car lots of converter and gear. the 292 is 244 duration at .050. Beware, BBC are known to wipe flat tappet cams. I have had good luck but historically, I have only installed small cams. Save the cash and go with a hyd roller around the late 220's- to early 230's at .050....you won't be disappointed.