a500 ?

I'd advise against the use of the A-500 , especially when it's going behind a nice , torquey motor like a 360 .

They have that beautiful lockup converter ( and , last time I checked , no one makes higher-stall converters for them ) ; and they were only available behind the 239 ( 3.9 Litre ) V6 and 5.2 Litre ( 318 ) V8 ; the 360 got the vastly-superior A-518 ( ad. seq. ) .

The A-500 is nothing more than a 904 with overdrive ; the 518 is an A-727 with overdrive .

The mods necessary to slip one of these in an "A" Body are very involved and quite extensive . Back in c.1991 , Rick Ehrenberg ( Mopar Action's Tech Editor ) ran an article wherein he and his cronies installed a 518 in Rick's 1974 Duster ( W2 340 , etc. ) .
It definitely wasn't a shade tree mechanic swap !

Now-a-days , there's the Keisler 4 speed auto . A bolt-in swap ( no trans tunnel interference ) .