The 305 was never a very high performance engine.
Even in the Camaro's, it was very weak compared to it's slightly big brother. It was a good inexpensive upgrade in the Camaro from the V6 and was still economically priced for those who didn't want to spring for the 350. Eventually, I think the 305 was completely replaced with the V6 in the Camaro and the only two options were the V6 and the 350.
It was a pretty weak workhorse in the full size trucks also.
I think on average, the 305 has been rated around 180hp...

1995 Trooper LS auto 3.2 DOHC /w SOHC intake
1989 Trooper 2.6 auto
1989 I-Mark RS DOHC 1.6
1991 Stylus XS DOHC 1.8