I have a 1984 5th Avenue, as far as I know in original stock trim. I've always thought that Mopar rwd cars from the early 1960's thru late 1980's had either a 904 transmission behind slant sixes and LA blocks and a 727 behind big block engines. It seems there are several variants of the smaller transmissions, 904, 998, and 999. How can I tell which variant I have?. I intend to haul an 1800 lb trailer with this car, I will of course put in a transmission cooler, and get my transmission guy to give it an overhaul, I have been told a deep oil pan would be a good idea as well. Also I've been told a lower ratio diff would be very useful. I have a V6 fwd Oldsmobile 88 that does a good job of pulling the trailer, my wife's 2 liter turbo diesel Peugeot manages ok too, but is at the high end of what it can safely handle. I had thought the 5th Avenue would be an improvement on both of these right out of the box, but it seems the gearing is too tall. Thanks in anticipation; Roger.