340 upgrades.

Yes its a little high but 10.5 was with .020 head gaskets. Today most are .040 thick and you can buy .060 thick one too. Each .020 will lower the compression about a half of point so if you use the .060 ones that give you 9.5-1 compression. It might even be ok with 10-1 but yeah thats pushing it. If the timing is back off a few degress it should be fine. The only heads you find today that are better are Eddy's or Indys heads. Those heads might be for unleaded gas, I am not sure. Think by 1972 the heads were made for unleaded gas but you could have harden seats put in I guess to be safe. You know if you are to spend money on head work maybe you should get Eddy heads. They love those 10-5 pistons cause aluminum heads knock a full point of compession down. Well not really but if 9-1 compression with iron heads are max for the type of gas being used then aluminum heads are 10-1 max for the same gas. Something about heat loss is why. Eddy heads have harden seats too. I would call or look at Indy heads, they help you out. They have everything too from 318 heads to the heads you have and also Eddy's and of course Indy's, but those are like $3000! Its www.aeroheadracing.com its a part of Indy heads company.