If you try a new pressure switch you still will be able to destroy your block. If you have one bar oil pressure but never get higher then that it will look ok for your pressure switch but the engine will die soon. Really don't be a fool and check pressure over whole rpm range. The cost isn't even that high!! For 26 pound you should check your base first, an engine with oil pressure. If you find out later its oil press you can trow away your "nnew" lifters too

Don't be a fool!