trying to connect coil over tube type temp gauge, 48 truck, the hole in the head is 3/4", was plugged with a bolt. the end of the tube that is to connect to the head doesnt have a bulb, instead looks like a small nipple. connected it to a flared reducer and it leaks coolant. an old head i have around seems to have this same nipple type welded to the head itself. also have bulb type unit but for older truck so wont fit in gauge cluster. any info appreciated, thank you, Dave in squamish B.C. canada.