I have a 1996 p38 4.0 us spec. and have been running both optima red top and yellow top.
when red top died I used a yellow top for the primary (and only) starting battery
I now have a dual (or in the process of) battery set up: Red/Yellow top optimas adjacent and placed longditudinal in the existing battery tray, using a solenoid battery manager from Wrangler products Portland OR.(I will post pics shortly)
Optima has all the information concerning the differences between red (2 types)/yellow/blue(marine) (2 types) batteries.
There are 2 types of blue marine batteries deep cycle / starting and starting.
There appears to be not much difference between the yellow and blue deep cycle/starting. except the addition of post/screw type terminals.
The other blue type is starting only.
I have had a lot of success with the optima (cannot tell the difference between red/yellow) when used for starting.
It should also be noted that there a 2 versions of the red top 1 with 750cca and the other 800cca.
I just brought a red top 800cca from Pep boys for $189.
Have only needed to replaced one red top in last 6 years of operation.
hope this helps
Thanks Theor, That was the answer I was looking for. How is the fit as they don't have a listing for our cars except for the Duralast Gold 34-DLG. In Arizona, its a hard life for batteries and I have been happy with Autozone's Duralast Red tops in my other cars *they are cheap and last as long as an Interstate battery*. I'm hoping my issue is the battery as its been charging for 3 hours and the charger's self test program hasn't thrown up an error. I'm not in the mood for troubleshooting an electrical drain issue on the P38 with temps touching 110f.
The fit is all right, with the exception that you cannot put the plastic battery cover, as the screw-in terminals gets too tall for the battery cover. Duralast Gold is probably a good battery, but I don't think it's worth the additional cost. If I remember correctly, my Duralast heavy duty cost only like $100. You simply can't beat that.
The gold they have listed for the 98 P38 doesn't have the same CCA as the one you have. However, the price seems to be comparable for a 3 year full replacement warranty and it is slightly shorter in height.
I ended up buying a Duralast Gold 27-DLG as it is a bigger battery (Slightly less CCA) than the other one and the height was just right. Otherwise 31-DLG would have been shorter and wouldn't have fitted under the top bracket without some sort of spacers under it.
Hope this helps someone looking for a cheap battery with a good warranty.