GEE....the "dicks" I hear of in this hobbie....
IT Does not matter what batteries you use.....you can use any thing from a old 1500 stick pack up to a ib 4200 matched pack !!!!!
If you are a back yard hacker ,just get the cheapest battery,but get anything over 3000 as anything lower will not give a very long run time,
and if you want to race they will be fine too.
I would get the 3800 ,..... BUT !!!!!!! ...as long as they are NEW !!!!,too many guys are selling batteries that are stuffed and you won't tell untill you use them.Some stuff in this hobby you might as well buy new as the price is nearly the same as new.
As for running your car,always check your car for heat,as this is what wrecks the car,Don't run it non stop on a hot day untill the battery is flat or on "thick grass".
Keep us posted on how your going