I was talking about on your non-PI motor, you posted about just a SC on your motor above. With PI heads & intake, decent cams, etc. you can get close to 300rwhp yes. Some are slightly over, some just under. With ported PI heads probably more power. I know with just the small XE262(non PI) cams on a non-PI motor it is around 20rwhp and 25rwtq gain.
It's just not worth the labor involved to do the heads/cams/intake on your motor. If you have the $$ to blow I guess. I do all my own work so it would not really bother me. If all you want is 290-300rwhp then just get a PI motor..cams..plenum..TB..and exhaust...tune