86 distributor upgrade

[1986brownjl]

Ok I have a 86 k10 with Qjet and original distributor. But I don't have vacuum advance on the distributor. All it has is a 4 pin connector that goes into the firewall. And on the dis. Cap there's 12 pos and ground. I'm wondering what are some upgrades for that distributor because I'm having pinging/detonation when im going up a hill in overdrive or with a load in overdrive going up a hill. Its only in overdrive. I was told it could be a timing issue or something else. But I'm wondering what are some upgrades for that distributor and what can cause the detonation.

Thanks