Double check to make sure your low/reverse band servo shaft 30 cent o ring is not leaking on the backside of transmission while you have the valve body out
You just have to remove the transmission mount and six bolts for tail shaft housing and rotate the tail shaft slightly to clear the tab
Just did this on my 71 Superbee after the transmission shop did not replace that o ring five years ago - It was hard and brittle
Fun laying on my back in the garage
Amazing how much of a mess that little o ring can leave on the garage floor after a winter hibernation
Trans shop did give me the o rings for free along with a newer servo shaft out of an overdrive transmission with double grooves or two o rings
Not a drop since but not a fun job to say the least on your back