According to this, the related options a
195/60-13, 175/70-13, 165/80-13

all based on the series I should use I assume.. does anybody know what would
be a standard series to use on an ez loader trailer?

"Floyd I Johnson" wrote in message
. ..

My question then is what is the comparable size to "A 78-13" in the
commonly
used sizing now (Canada).

Here's a link to a table that might help you:
http://www.turbinecar.com/tires.htm