Better that you asked about the oil pressure switch thread size. Older B21/23 cars used a simple pipe thread switch common to many cars. Your '92 has a different thread--metric I'd guess-and is sealed by a sealing washer rather than the thread.
The simplest oil pressure gauge would be a strictly mechanical unit with only a pipe going directly to the oil pressure port.
Unless you do lots of tune-up work a digital timing light with adjustable advance/retard and rpm display would be an unnecessary expense. A simple induction timing light could probably be had for a few dollars at a yard sale should suffice. Over the years I've accumulated 2 or 3 cheap ones (left in cars I've purchased) in addition to the professional model I bought for my tool box years ago and would be happy to clear some room--surely others have done the same. -- Dave