If it was done properly for gas only it will have very high compression, run a gas cam, hardened exhaust seats and a re-graphed dizzy. Some or all of this may not be done, you'd have to check it. If it is high compression you may find it pings even on 98 fuel. If it is OK compression wise then probably only the dizzy needs fixing - just get a HEI dizzy and coil off a blue/black motor. If it has a gas cam you may want to change that too.