Power steering heat exchanger
4.3 v6 cobra
Howdy, welcome aboard.
I have to assume that you currently have a freeze damaged PS cooler?
ANY marine cooler will work. Doesn't have to be OMC.
Yes, you probably could switch to an air cooled one but you'd want to put some air on it (run your bilge fans continuously or add an additional fan etc)....
It's likely not worth it though IMHO, ..........water--oil coolers are available everywhere new and used and are not all that expensive.
Regards,
Rick