Ther is a couple possibilities, 1)... When you had dash apart a wire for the oil pressure switch broke or came loose( going to the light in the dash)..or the PSI switch itself maybe bad....2) the regulator,even tho it " looked god" May need rebuilt/replaced..,or possibly the Diaphram in the air mixer needs replaced,just a few things to check.....on the back of the IMPCO. regulator(probably a model J?) there is a 1/8 pipe plug,put a pressure gauge here and see what your pressure is,should be around 2-3 PSI I believe.....IF you plan on replacing the regulator,I recommend installing a IMPCO Cobra model regulator,they are more reliable than the model J,little more $ put worth it in the long run,TRUST ME