Need help with 8388 ready to run distributor

416 stroker engine running 24 initial with 10 degree bushing.Just wanted to add 10 degrees timing at idle and cruise.If you run 34 degrees total the vac adds 20 degrees making total 54 degrees.I think i am going to make a plate to bolt in dist to keep it from advancing the vac arm all the way.They should put an adjustable one on it like mallory