You can look this up in the literature (Chassis manual, etc.) I believe the quoted number was actually 280? Anyhow, this is relatively meaningless as methods and measures have changed. It's a complicated question as it turns out.
If you have the 4 barrel engine that’s what it’s “rated” at. Consider it to be an estimate. 2 barrel engine is less
In real world modern dyno conditions the 315 Hp SP code 350 rated engine is about 230 HP. So I would guess the 69 engine high compression engine would be about 200 HP. A 350 with a TA-212 cam and some head porting is 350 Hp.
and with that stock engine you can still beat on 350 Chevy's that are stock also, and with a small cam...see ya!