A500

when you get it out or get under it just compare it,,either way they will both work,since they are over drive 4th being a reduction,first or low gear is lower then a 904/727,making it launch/leave from a standing start a little quicker,,,we are puting a 518 in a street rod behind A desoto hemi, in an A body,you will probably need to do a little cutting to the tunnel to make room for the over drive /tail shaft unit,,unless this is some low production big dolar car,,it is wel worth the effort for driveability and fuel mileage gains,,

i cant remember the year cut off,,i believe it is 96 and earlier,,,look at the plug if it is a 2 pin plug it is a non lock up converter,if it is a 3 pin plug the converter locks up electricly,,
you wil need to have some body that knnows the conversion of the over drive switch/and the hydralic pressure switch conversion,,,we havent gotten that far yet with our 518,,the trans wont act correctly if you just put a switch in line for the over drive,,you need to do some hyd pressure plumbing,from what i have heard its no big deal,,sory i dont have all the corect details,,,,just getting started with out convsersion,,,hope this helps a little,,,,dont let it scare ya from doing it,,,it works,ive seen plenty of street rods with this conversion,,,