In the last 3 weeks I've had to boost the batteries 3 times to get the Pajero to start (after 2 days at minus 20 or so). No block heater. Starts right away when it's warm of course. I get about 3 or 4 attempts of 15 to 25 seconds before it dies. While i'll be installing a battery warmer it looks like it may be time to replace the batteries . I have no history on the existing ones, one has japanese writing, the other north american.

So what type should I be getting- one with the highest cold starting amps I can fit in the tray, or
what? closed/sealed cell vs the type with caps? Some catalogs list the batteries by vehicle type, but I don't know if this has to do with physical dimensions or other electrical characteristics.

Should I replace both at the same time?

What brands are recommended and to be avoided?

Pros and cons of a deep cycle battery? They were recommended back when I had a 8K# Warn winch on a Bronco in the 80s?

Again, grateful for any advice.