Lockup converter compatibility

I recently swapped a magnum 360 in my 78 cordoba. I have the correct balancer and flexplate with 360 magnum weights and ordered a nuetral balance 727 converter. Since the swap I have been having engine vibration at cruising speed that is driving me crazy. After exhausting all options I learned that in 78 they switched to a lockup transmission. Could this be causing my vibration and if so am I able to use the 46re lock up converter that came with the magnum motor or do I need to order a 1978 318 converter?