farmall130

Hello, I'm new to this forum, usually hang out on the GM diesel forum. Got an issue I need some help with please.
I have a 1979 Chevy C-10 2WD with a replacement Goodwrench 350 (your basic 8.5:1 replacement) in it. It has been a great engine, doesn't use oil and has probably about 60-70K on it. Last year going down the road everything was fine and it stuck an exhaust valve. The piston pushed it back up without hurting itself, and my buddy replaced the guide and valve and of course, ground the seat. It has worked fine. Was the #5 cylinder.
Here we are a year later and it stuck one Friday on the other side, on #4.
I've heard everything from unleaded gas to type of oil as a cause. This engine is VERY clean, the stuck valve is not gaulded, neither was the last one. I use Havoline 10W-30 oil.
It's gonna need the same as before, new valve, seat ground, new guide and it bent the pushrod. Anybody got any experience with this? Would running an oil additive help? This is my knockaround truck, it does not get abused and gets serviced regularly. Thanks for your help.