Shift points on a 700r4?

my shift points from my 700r4 are at 15, 30 and then at 60 mph. to me i think 60 is to high because it is starting to scream at 53 on up before it does shift into overdrive. is there any thing i can do to make it shift around 45 to 52. or is there a recommendation on where the shift should be. i do a lot of town driving. 1970 monte carlo. thank you