magnum 360 into a 74 duster that had a slant 6

Ok.. Then why does the book for a 95 dodge 1500 call for a 91 gram weighted converter?
It can be done either way. You can use a neutral balanced converter with a stock magnum weighted flex plate which is def the preferred and easiest method or you can use a weighted converter with a neutral balance flex plate. I’ve done it both ways and find it much simpler using the stock magnum weighted flex plate. There’s no guess work in weights and no vibration issues this way, imho.