Help Choose new Plugs for worked 360

Is your vacuum advance hooked up to ported vacuum or manifold vacuum? Disconnect it temporarily, put a vacuum gauge on your manifold with a long enough tube to have it inside the car for later testing. Keep advancing your timing until your vacuum quits getting higher. That's your initial timing. Weld up the slots and use a chain saw file and a timing light to limit your total timing to 34 or 36 whichever it likes better. Make sure your centrifugal advance is all in at your highway cruising speed 55, 60 or even 65 etc.

Make sure you don't get too much vacuum advance. You may have to weld up the stop and file it to get it dialed in. Re connect it it to manifold vacuum only, then make sure you have 50 to 52 total cruising down the highway 55-60 at barley any throttle.

The vacuum advance should drop to zero as soon as you punch it or take of with significant throttle helping avoid gas knock. Adjust your total mechanical timing lower if you are gas knocking at all.

This will improve your off idle drivability dramatically and give you better mileage on the highway and around town.