I went with the 518 trans.. basically its a 727 with
OD and lock up.. I eliminated the lock up so I could
run a high stall regular 727 conv... the 518 has
a .69 OD ratio.... and the good thing.. it bolts right
up to a small block... they are a heavy trans and its
longer than the 727 with the OD in the tail shaft..
if you get one of the earlier ones all you need is
a switch to turn on the OD or the lock up if you wanted
to keep that... the reason I dumped the lock up is
due to the conv.. you cant get a high stall that will
have lock up and live(lack of clutch area in the conv)