How many using an A500 overdrive ?

How many have installed an A500/42h overdrive transmission ? Why did you choose it over the A518/46h overdrive ?
How has it held up for the way that you use your car ? Would you choose the A500/42h again/ or upgrade to the larger A518/46h ?
Trying to poll those that have been there/done that. To help me make a informed choice. Thanks...please ad any comments.
My vehicle is a 1964 Dodge A100. With a 318 mostly stock. DD , cruiser.