any way you can use the 2tg pistons on the 3t rods
No, you can't. The extra 8mm throw of the 3T crank is accommodated by a wrist pin height adjustment for 3T pistons compared with earlier 2T pistons. As all the rods are the same length 2T pistons with 3T crank will extend beyond deck height at TDC.
You could use 3T-C pistons with 2T crank though, although your resulting compression will be about 4ish:1.. =/ and 3T-G pistons lower again. Be great if you want to run 30PSI all day long though.
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because the pistons are already fly cut and high compresion
3T-C pistons on 78mm bottom end with 2T-G head often yields around 10.5:1, I believe. How much compression would you like to run?