[Roadsters] oil pressure guage woes

[steven boortz]

hi everyone
thanks in advance for any help you might offer.
i bought a new mechanical oil pressure guage (AutoMeter) because my original guage was giving some funny readings.  i removed the original sender from the block, and attempted to insert the adapter (1/8 NPT female to 1/8 BPST male).  i cannot thread the adapter into the block.  at all.  it won't even start.  the 1/8 NPT compression fitting that would go into the adapter won't go into the  block either.  the original sender unit screws in by finger strength, no problem.  i cannot tell by holding them together, whether the threads on the original sender are closer to the 1/8 NPT or 1/8 BPST, they are that close.
any ideas?
thanks again
steve
675MIZU