HP gain of 10.5-1 pistons vs 8.8-1 in a 273.

Looking good. If your short block is together I wouldn't mess with it. The Egge pistons will get you about 9.6/1 with milled heads. Run what you have and it will perform well. If you want a tire smoker build yourself a 400 horse 318, a 340 or a 360 but with those combinations you may need upgrades to the drivetrain.
Thanks Mike, I'll go with it as is.