Need help fast! Oil pressure gauge install trouble

[mdost03]

OK, I am very confused by this car. I'll tell it slowly so everyone can understand.

I know our cars use a 1/8" BPT thread pattern on the oil pressure sending unit. I bought an Autometer Ultra-Lite gauge from Summit and I am trying to install it. The sender has a 1/8" NPT thread type so I bought a 1/8" NPT to 1/8" BPT adaptor from them (Autometer) to use to install the sender. I removed the stock sender with no problem and I go to install the 1/8" NPT to BPT adaptor and it won't screw in. Will just barely start and then stop like it is cross-threading almost. Tried screwing in just the 1/8" NPT sender from the gauge and it does the same exact thing. Tried screwing the stock sender and it screws in just fine. Checked the package and I have the right adaptor. Weird thing is, the stock sender with the 1/8" BPT threads screws into the 1/8" NPT adaptor side with no problem, screws in about as far as the aftermarket gauge sender with the 1/8" NPT threads.

Now here is my question, should I try forcing the BPT adaptor on (don't feel comfortable doing this) or should I use this 1/8" NPT tap I have here and thread it into the oil pressure sender hole? The tap goes in about 3-4 full turns before stopping. I've read on tuners when I did a search that people have tapped the BPT thread pattern with an NPT thread pattern no problem, but wanted to see what everyone's opinion or experience on this matter is. Thanks and quick replies are appreciated since I was planning on installing this gauge today and get it out of the way so I can put the engine back together this weekend.