2 PSIG Service to Pool Heater

I have a 2 PSIG gas service to a regulator at the pool heater location.  The size of the line to the regulator is about  5/8" or 3/4" at a distance of about 45 feet to the meter.  A few years ago I had the gas system upgraded from a conventional  low pressure system with a larger pipe size.  It servided a 22 year old 250K Teledyne Laars Lite pool heater that is no longer working.  I’m considering replacing it with either a Raypak 266K or 336K with electronic ignition.  My pool has 680 sf of surface area and about 27,500 gallons, and I live near Birmingham, AL.  Is my gas service adequate?  Which size model do you recommend?  Is the cupro nickel worth the extra expense for a chlorinated pool?  Thanks.