Just another thought if your changing distributors. Mine was very loose (everyone says they all are) and wobbled about a bit in the block.
However, there is an upgraded ‘Distributor Housing’ aka the ‘sleeve’ that sits into the block which the distributor fits into available from TOC parts, which has an internal and an external ‘O’ ring so when fitted, the distributor is a far more ‘snug’ fit with minimal ‘wobble’
Part number is D48E @ £15.89 and well worth fitting.
Ended up ‘feeling’ for the correct alignment on the timing by hand, by listening to the engine, rather than via a strobe light as my white markings weren’t very good 😆