You WILL be able to pull the distributor out of the block, no issue whatsoever. The retaining device is on the oil drive shaft and is designed to keep it located on the oil pump when folks pull the distributor. The locating device cannot be relied upon as it can fail over time, simply be ineffective from day one, or may have been omitted during the engine (re) build as it serves no purpose if the engine is being rebuilt on a bench with the sump off.
As above, give it a Google. The Yanks have been pulling distributors out of SBF ever since the 1960's - and it's far from rocket science.