I used the L98 HO Aluminum vette heads on my 305 I had in my 86 Elky. they have 58cc chambers 1.95/1.5.
I had the comp cams 256X in it. car ran 13.70s with 3.08s . worked real well. Another great, maybe better option for 305 is vortec heads.
I had KBpistons in mine & with 58cc head came to right at 10.2:1. I was real happy with it.
Dollar for dollar 350 or more makes more power than the 305, but the 305 can perform if done right.