Dont fix the block fix the part you do not have already. First off with 64 cc you will have more than 8:1 you should be able to buy heads in 58cc.
When i run my 350 numbers with 64 cc heads i get much diferent numbers.
United Engine & Machine Co. Incorporated
Check this site. Off the top of my head the stroke for 350 is 3.48 with gasket of 4.063 min and .043 thick with .025 deck and +5 cc dish i get 9.7:1 unless your dish is even more than 5 cc. You will need to actually measure i think once you run all the numbers you can rasie the compression with thin copper gaskets if need be but try to aovid it. Also gas is **** these days better to stay safe. 10:1 on iron heads is pushing it.