A low budget adjustable timing tab is not too difficult to install IMO (and they are cheap.) Make a home made stop from a spark plug and be on your merry, or Mary, way (
). Either way I would n't lose any sleep from it. If you don't want to goof with the adjustable tab, then tune it by driving until it pings and back it off a couple of degrees and put the nitrous to it. All you need is a reference point to know how far your retarding it when the nitrous hits. Either way, you don't need to pull a head.