307 pinging... 305 heads

[70c10guy]

Hi all, I need help!

I recently swapped heads, intake and carb. As well as tranny in my truck!

-305 #416 heads stock
-edelbrock performer
-4150 holley dp
-s10 t5 tranny

My issue is I am getting a light ping under load. I was originally running 10 degrees btdc but it was way too much timing when going up hills with a load on the engine. I kept backing it down 2 degrees at a time and now I'm at 2 degrres btdc. That's what the sticker on thetruck calls for but it is still pinging very slightly. Not as much as it was. Should I keep going down on timing or no? What other options do I have!!? Running sunoco 87 octane and thought that would be fine because compression isn't crazy on these 307's even with the 416 heads.