does any one know what the tread size is for the oil pressure switch on a 351w windsor engine and who makes a t piece to have an oil pressure gauge and switch
1/4" npt for the thread in the block, tee piece available in brass / steel from most places that sell hyd hose & fittings, or if you have an earls or aeroquip supplier in your area.
Be careful when developing a "tree" to adapt various sending units or hoses. I have seen the various short lengths of pipe fracture at the threads from vibration and shock, especially if using Brass.
You an get them new from www.cjponyparts.com They are chrome plated, but they also sell the OEM zinc plated piece. They are easily drilled and tapped for additional ports. Do a search on that site for "oil pressure log"