Here ya go.
clicky
Type in part# H618CP30
9.38:1 compression with 76cc heads.
Values are calculated with a virgin block 9.250" deck, .025" piston deck height and a .030" compressed head gasget.
That would give a quench of .055".
That is all ballpark figures, you would have to measure it all out to get the final ratio.
Another
click
A good read on quench.
click
I have a set of Speed-pro's that I linked.
Now that I have to use another block and it will be .030 over I am going with the flattop 2 valve releif version.
8.68 with 76cc chambers, mine are prolly closer to 74 and I am going with a .050" quench. That should put me at 9's door. Which is what the cam I am going to use recomends.
I have never tried to soup up a TBI plant but I would think that 9.0:1 would be plenty, if the sensor detects detonation it will retard the timing and it will run like crap, especialy with todays flavor of fuel.
No need to build a plant that you can't take full advantage of.
Besides just ditching the stock dish pistons for flattops will be a good upgrade.
Read the clicky on quench and it goes into better detail on that.