Stock battery group # is H-7 or R-94. Not to many replacements in that # out yet but R-49 has same or larger crank amps and reserve minutes. R-49 group is just 2 inches longer but will fit in the trunk and has the correct trunk VENT TUBE. R-94 fits Mercedes and BMW trunk mount batteries. R-94 size is available in many brands.It is a better value than optima which to me is over priced and over rated doesnt last any longer than any normal battery.
I did look at the R-49, but the PC1700 is nearly the same dimensions
as 94R and there is no comparison between it and OEM or the group 49.
Funny about the Optima, it was the only battery that stopped my
Grand Prix from eating alternators. I had a 97 with the smallish
CS cased 105 amp alt that was mounted on top of the exhaust
manifold. That design wasn't thought through well. There was
very little surface area for cooling, and then to have it near the
main exhaust for the engine. Went through 2 until I bought the optima.
Drove the car 6 years and traded it in with the optima still in it.
not sure I want to spend the extra for the PC1700 ATM though, it's about
$70 more than the optima.