Parallex 7300 series is a single stage charger, These do a slow job and either never fully charge the batteries or over charge them (Parallex has decent regulation so they do not often over charge)
For two Group 27's I'd not go over 60 amps. the 45 is really a good size but you could go up to 60
I'd replace the "GUTS" of the 7300 with a Progressive Dynamics 9200 (9245 or 9260) the reomte dongle is optional on this model
Or if it's cheaper a 9100 with the optional charge wizard (Which is also a remote dongle) (The wizard is built into the 9200)
These are top of the line 3-stage chargers and will recharge the batteries in 6-8 hours.